Download Dynamic Function Test

Title: Dynamic Function Test Handbook
Authors Names:
Jonathan Clayton
Scope: Clinical Chemistry laboratory service users
Classification: Information
Replaces:
To be read in conjunction with the following documents: Clinical Chemistry Laboratory Handbook
Unique Identifier: BIO-I-P-011
Review Date: August 2018
This document is no longer authorised for use after this date
Issue Status: Approved
Authorised by: Joanna Borzomato
Issue No: 3
Issue Date: August 2016
Authorisation Date: August 2016
Document for Public Display: Yes
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Clinical Biochemistry
Dynamic Function Test Information for Users of the
PAWS Biochemistry Service
Pathology at Wigan and Salford
Q-Pulse Ref: BIO-I-P-011
Q -Pulse Revision
No: 3
Authorised By: Joanna Borzomato
Page 2 of 38
Contents
Dynamic Function Tests......................................................................................................................................3
24 Hour Urine Collection ................................................................................................................................4
Investigation of Anaphylaxis...........................................................................................................................5
Calcium Excretion Index (Calcium Clearance Ratio) .......................................................................................6
Creatinine Clearance ......................................................................................................................................7
Cushing’s Syndrome .......................................................................................................................................8
24 hour Urinary Free Cortisol (24h UFC) ....................................................................................................9
Overnight Dexamethasone Suppression Test (ONDST)........................................................................... 10
Low Dose Dexamethasone Suppression Test (LDDST) ............................................................................ 11
High Dose Dexamethasone Suppression Test (HDDST) ........................................................................... 13
Glucose Tolerance Test................................................................................................................................ 15
Mixed Meal Test for Investigation of Reactive Hypoglycaemia .................................................................. 18
Glycosade Loading Test ............................................................................................................................... 20
Growth Hormone Suppression Test (GTT with Growth Hormone) ............................................................. 22
Glucagon Stimulation Test........................................................................................................................... 24
Arginine Stimulation Test ............................................................................................................................ 26
Clonidine Stimulation Test........................................................................................................................... 27
Gut Hormone Profile ................................................................................................................................... 29
48/72 hour Prolonged Supervised Fast (Insulinoma) .................................................................................. 30
Luteinising Hormone Releasing Hormone (LHRH) or Gonadotrophin Releasing Hormone (GnRH)
Stimulation Test........................................................................................................................................... 32
Short Synacthen Test (Addison’s Disease Screen)....................................................................................... 34
Short Synacthen Test (Congenital Adrenal Hyperplasia)............................................................................. 35
Thyrotropin Releasing Hormone (TRH) Stimulation Test ............................................................................ 36
Water Deprivation Test ............................................................................................................................... 37
Page 2 of 38
Clinical Biochemistry
Dynamic Function Test Information for Users of the
PAWS Biochemistry Service
Pathology at Wigan and Salford
Q-Pulse Ref: BIO-I-P-011
Q -Pulse Revision
No: 3
Authorised By: Joanna Borzomato
Page 3 of 38
Dynamic Function Tests
This handbook deals with a selected number of the most frequently requested dynamic tests. For details of
other tests not detailed in this handbook, please see the SRFT Endocrinology Investigation Manual or
contact the Duty Biochemist on (0161 20) 68212 for advice.
These tests, properly performed, provide more information than can be obtained from single
determinations. Incorrectly performed dynamic test results inconvenience the patient, mislead the clinician
and waste precious laboratory resources.
Since many tests involve accurate collection of 24 hour urine specimens this section explains the
procedures.
Other tests are arranged in alphabetical order.
Page 3 of 38
Clinical Biochemistry
Dynamic Function Test Information for Users of the
PAWS Biochemistry Service
Pathology at Wigan and Salford
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Authorised By: Joanna Borzomato
Page 4 of 38
24 Hour Urine Collection
Accurately timed, complete urine collections are a vital part of many tests, particularly those concerned
with renal function. Careful attention to detail, especially by the ward, is necessary.
Obtain a urine container with the correct preservative (see PAWS Biochemistry User Handbook). Choose a
convenient time to start the collection usually in the early morning, e.g. 8am. If collecting on a ward, it is
convenient to have a routine time for starting all collections. If results are required on the day of
completion, specimens must be received in the laboratory by 10am.
Day 1
8am
Day 2
8am
Ask the patient to empty their bladder completely and discard this
specimen.
Thereafter collect all urine passed into this container for the next 24 hours.
Ask the patient to empty their bladder completely and add this specimen to
the collection.
Collect no more urine.
Ensure the sample is fully labeled:
PATIENT’S FULL NAME
DATE OF BIRTH
HOSPITAL NUMBER or NHS NUMBER(if available)
START TIME AND DATE OF COLLECTION
FINISH TIME AND DATE OF COLLECTION
Notes
1. Ensure that urine and faeces are passed separately.
2. If the container is full before completion of collection, use a second one with the same
preservative, and send both to the laboratory.
3. If any specimen of urine is not collected or accidentally discarded during the collection, discontinue
the test and start again
Page 4 of 38
Clinical Biochemistry
Dynamic Function Test Information for Users of the
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Investigation of Anaphylaxis
Indication
In the investigation of suspected Anaphylactic reactions.
Preparation of Patient
None
Sample requirements
Collect two 5mL EDTA blood samples (red top Sarstedt Monovette), one for full blood count and one for
mast cell tryptase, at the following times:
 Initial sample as soon as feasible after resuscitation.
 Second sample 1-2h (no later than 4 hours) after onset of symptoms
 Third sample either at 24hrs or at convalescence (e.g. in follow up allergy clinic). This is a measure
of baseline tryptase levels as some individuals have higher baseline levels.
Transport to laboratory and analysis
Ensure that the samples are clearly labelled with patient details and time and date.
Transport to the laboratory immediately after collection. Samples for mast cell tryptase are analysed in
Salford Immunology.
Documentation
This should accompany the request and should include: time and date of reaction; surgical procedure,
drugs administered, clinical manifestations, previous medical/anaesthetic history (if known), any risk
factors (e.g. penicillin allergy) and management of reaction and outcome.
Interpretation
Transiently raised tryptase is seen within 30-180 minutes of systemic acute anaphylaxis. It is chronically
raised in Mastocytosis. A baseline sample (24 hr post event) is therefore essential for interpretation.
References
NICE CG 134 Anaphylaxis: assessment to confirm an anaphylactic episode and the decision to refer after
emergency treatment for a suspected anaphylactic episode. 2011
Management of a patient with suspected anaphylaxis during anaesthesia, The Association of Anaesthetists
of Great Britain and Ireland 2009
Suspected Anaphylactic Reactions Associated with Anaesthesia, Association of Anaesthetists of Great
Britain and Ireland 2008
Assay information: Adverse (Anaphylactoid) reactions to Intravenous drugs, Supra-regional Assay Service,
Sheffield.
Page 5 of 38
Clinical Biochemistry
Dynamic Function Test Information for Users of the
PAWS Biochemistry Service
Pathology at Wigan and Salford
Q-Pulse Ref: BIO-I-P-011
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Authorised By: Joanna Borzomato
Page 6 of 38
Calcium Excretion Index (Calcium Clearance Ratio)
Clinical Use
Investigation of suspected familial hypocalciuric hypercalcaemia (FHH) in patients with hypercalcemia.
Preparation of Patient
The patient is fasted overnight for 10-16 hours (water is allowed). The patient should not be taking any
diuretics during the test, and should be vitamin D replete.
Procedure
1 Collect a random sample of urine passed between 9-11 am (in white top plain container).
2 Collect a blood sample (8ml brown top gel-tube) during the same time
3 Send the urine and blood samples together to the Laboratory clearly writing Calcium Excretion Index on
the request form (Biochemistry section).
Interpretation
Calcium Excretion Index Result
Interpretation
≤0.013
Familial Hypocalciuric Hypercalcaemia (FHH)
0.013 – 0.037
Equivocal – other investigations and referral to
endocrinology
≥0.037
Primary Hyperparathyroidism
Calcium excretion index is calculated as:
𝐶𝐸𝐼 =
𝑈𝐶𝑎 × 𝑆𝐶𝑟
𝑈𝐶𝑟 × 1000
Where:
UCa = urine calcium concentration in mmol/L
SCr = serum creatinine concentration in µmol/L
UCr = urine creatinine concentration in mmol/L
Reference
Foley KF, Urine Calcium: Laboratory Measurement and Clinical Utility, Labmedicine 2010; 41(11):683-686
Page 6 of 38
Clinical Biochemistry
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Page 7 of 38
Creatinine Clearance
Requires a 24 hour plain urine (see guidance on 24 Hour Urine Collection) and a paired serum for urea and
electrolytes (U&E) taken as soon after completion of the collection as possible. The urine and serum
samples should be delivered to the lab together.
Creatinine clearance is calculated as:
𝐶𝑟𝐶𝑙 =
1000 × 𝑈𝑉𝑜𝑙 × 𝑈𝐶𝑟𝑒𝑎𝑡𝑖𝑛𝑖𝑛𝑒
𝑈𝐷𝑢𝑟𝑎𝑡𝑖𝑜𝑛 × 60 × 𝑆𝐶𝑟𝑒𝑎𝑡𝑖𝑛𝑖𝑛𝑒
Where:
CrCl = creatinine clearance in mL/min
UVol = urine volume in mL
UCreatinine = urine creatinine concentration in mmol/L
UDuration = duration of urine collection in hours
SCreatinine = serum creatinine concentration in µmol/L
Page 7 of 38
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Cushing’s Syndrome
Note: Oestrogens [oral contraceptive pill (OCP) and hormone replacement therapy (HRT)] are known to
increase cortisol binding globulin (CBG) and thus may over-estimate serum cortisol levels. It is
recommended that OCP/HRT is stopped 6 weeks prior to testing.
Investigations
The SRFT Endocrine Investigation Manual contains extensive information and protocols for the
investigation of Cushing’s Syndrome. It is strongly recommended that if Cushing’s Syndrome is suspected, a
Clinical Endocrinologist is contacted prior to commencing investigations.
Guidelines for the investigation of Cushing’s Syndrome have been published by the Endocrine Society in
2008. The following algorithm and protocols for first-line testing shown below are taken from or based on
these guidelines.
Measurement of cortisol in saliva is not currently available at PAWS, thus firstly 1-mg overnight
dexamethasone suppression test (ONDST) then 24-hour urinary free cortisol (24h UFC) are recommended
as first line tests.
Page 8 of 38
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24 hour Urinary Free Cortisol (24h UFC)
Preparation of Patient
The test can be performed fasting or fed.
Contraindications
Ensure patient is not taking steroids in any form (including creams and nasal sprays). Interpretation may be
difficult if performed at a time of intercurrent illness, when cortisol secretion would physiologically increase
anyway.
Procedure
See guidance on 24 Hour Urine Collection
Interpretation
UFC should be less than 180 nmol/24 hr. If greater levels are confirmed on 2 occasions then the patient
should undergo further investigation. The sensitivity and specificity of this test are fairly low and hence 3
UFCs are required to exclude Cushing’s syndrome. If all 3 UFCs are normal then it is extremely unlikely that
the patient has Cushings syndrome. Conversely, if the cortisol level on one sample is four times the upper
limit of normal then Cushing’s syndrome is highly probable. False positive results seen in patients with
pseudocushings, alcoholism and PCOS.
When 3 UFC are performed: 3.3% false positive rate, 5.6% false negative rate.
Notes
Urinary free cortisol is measured using LC-MS/MS.
Page 9 of 38
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Overnight Dexamethasone Suppression Test (ONDST)
Preparation of Patient
The test can be performed on an in or out-patient basis and fasting is not required.
Contraindications
 Pregnancy
 Epilepsy
 Suspected cyclic Cushing’s Syndrome
 In the above cases, 24-UFC is recommended as the first line test.
Procedure
1 Dexamethasone (1 mg) is given orally at 11pm.
2 A single blood specimen (serum gel tube – brown top Sarstedt Monovette) is collected for serum
cortisol between 8am – 9am the following morning.
Interpretation
Normal individuals suppress serum cortisol to <50 nmol/L.
Patients who fail to suppress should be tested with the low dose dexamethasone test and referred to
endocrinology.
Notes
a)
Patients on enzyme inducing drugs (e.g. anticonvulsants and rifampicin) may rapidly metabolise
dexamethasone and give false positive results (i.e. no suppression). Women on oestrogen therapy may
not adequately suppress due to increased cortisol binding globulin.
b)
Normal subjects rarely (2%) fail to suppress with overnight dexamethasone. False positives may occur
with: depression (due to the development of a reversible glucocorticoid resistance), severe systemic
illness and patients with renal failure on dialysis. Patients with simple obesity do not have an increased
rate of false positive results.
c)
In patients with glucocorticoid resistance syndrome basal ACTH and cortisol levels are elevated and
only partially suppressible with dexamethasone. The patients do not look cushingoid, although women
are hirsute because of high adrenal androgens secondary to elevated ACTH levels.
d)
Alcohol must be rigorously avoided for a minimum of 3 days prior to this test (alcohol-induced pseudoCushing’s syndrome)
Page 10 of 38
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Low Dose Dexamethasone Suppression Test (LDDST)
Indication
Second line test for Cushing's syndrome.
Preparation of patient
This is usually an inpatient test with no patient preparation required. Occasionally the test can be done as
an outpatient (if you are confident that the patient is likely to take their tablets on time). Patients require a
9am serum cortisol and plasma ACTH prior to the first dose of dexamethasone. The patient must be able to
take the dexamethasone exactly 6 hourly for the next 48 hours. A repeat 9am serum cortisol and plasma
ACTH is required 6 hours after the final dose of dexamethasone.
Stop all oral oestrogen therapy (OCP or HRT) 6 weeks prior to test. Patients on sex steroid implants might
generate results that are difficult to interpret.
Contraindications
 Patients on enzyme inducing drugs e.g. anti-convulsants may rapidly metabolise dexamethasone.
 Oestrogens (e.g. pregnancy, HRT or COC) may induce cortisol binding protein and artificially
increase total cortisol levels.
 Care in diabetes mellitus and patients who are psychologically unstable.
Procedure
Day
Time
ACTH
(Li-Hep plasma)
Cortisol
(serum sample)
Dexamethasone
0.5 mg orally
1
9am



2
3
3pm

9pm

3am

9am

3pm

9pm

3am

9am


NOTE: Samples for ACTH MUST be received by the laboratory within 15 minutes of venepuncture.
Page 11 of 38
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Interpretation
If the day 3 9am cortisol value is < 50nmol/L the patient has shown suppression. Failure to suppress is seen
in the autonomous secretion of cortisol found in Cushing's syndrome. However, since there are several
common conditions associated with impaired cortisol suppression following a LDDST (e.g. morbid obesity,
depression), the result should always be interpreted in conjunction with the degree of clinical
suspicion/signs or symptoms of patient.
Sensitivity and Specificity
Suppression in patients with Cushing's syndrome is rare (2-5%). In some reported cases metabolism of
dexamethasone occurs slowly and so higher circulating levels of serum cortisol than expected are found.
This test is more specific than the overnight suppression test with a lower false positive rate. Failure of
suppression in patients may be seen in patients with systemic illness, endogenous depression, or on
enzyme inducing drugs e.g. phenytoin or rifampicin.
References
Newell-Price J et al., The Diagnosis and Differential Diagnosis of Cushing’s Syndrome and Pseudo-Cushing’s
States. Endocrine Reviews 1998; 19(5):647-672
Page 12 of 38
Clinical Biochemistry
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High Dose Dexamethasone Suppression Test (HDDST)
Indication
Third line test for distinguishing between pituitary and ectopic secretion of ACTH. ACTH-producing
adenomas of the pituitary retain some responsiveness to the suppressive effects of dexamethasone, unlike
ectopic ACTH secreting tumours, which do not.
Preparation of patient
This is usually an inpatient test with no patient preparation required. Occasionally the test can be done as
an outpatient (if you are confident that the patient is likely to take their tablets on time). Patients require a
9am serum cortisol and plasma ACTH prior to the first dose of dexamethasone. The patient must be able to
take the dexamethasone exactly 6 hourly for the next 48 hours. A repeat 9am serum cortisol and plasma
ACTH is required 6 hours after the final dose of dexamethasone.
Stop all oral oestrogen therapy (OCP or HRT) 6 weeks prior to test. Patients on sex steroid implants might
generate results that are difficult to interpret.
Contraindications
 Patients on enzyme inducing drugs e.g. anti-convulsants may rapidly metabolise dexamethasone.
 Oestrogens (e.g. pregnancy, HRT or COC) may induce cortisol binding protein and artificially
increase total cortisol levels.
 Care in diabetes mellitus and patients who are psychologically unstable.
Procedure
Day
Time
ACTH
(Li-Hep plasma)
Cortisol
(serum sample)
Dexamethasone
2.0 mg orally
1
9am



2
3
3pm

9pm

3am

9am

3pm

9pm

3am

9am


NOTE: Samples for ACTH MUST be received by the laboratory within 15 minutes of venepuncture.
Page 13 of 38
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Interpretation
Suppression of cortisol levels by greater than 50% occurs in 75% of patients with Cushing’s disease, 10-15%
of patients with ectopic ACTH secretion and 0-6% of patients with adrenal tumours. The day 3 9am cortisol
after the 48hr test is considered to be the most sensitive means of differentiating between Cushing’s
disease and ectopic production.
References
Newell-Price J et al., The Diagnosis and Differential Diagnosis of Cushing’s Syndrome and Pseudo-Cushing’s
States. Endocrine Reviews 1998; 19(5):647-672
Page 14 of 38
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Page 15 of 38
Glucose Tolerance Test
The diagnosis of Diabetes Mellitus should be made according to the World Health Organisation Guidelines
2006 and the World Health Organisation Guidelines on the Use of HbA1c in the Diagnosis of Diabetes
Mellitus 2011.
Glucose tolerance tests (GTT) are rarely needed to diagnose diabetes mellitus. If the patient has suggestive
symptoms, measure the fasting blood glucose. A fasting plasma glucose of 7.0 mmol/L or above on two
different days is consistent with diabetes mellitus even in the absence of symptoms under the 2006 W.H.O.
criteria. These criteria also defined a new category of intolerance called Impaired Fasting Glycaemia (IFG),
where fasting plasma glucose is between 6.1 and 6.9 mmol/L. The Guidelines state that people with IFG
should have a full GTT to determine tolerance status.
Glycated haemoglobin (HbA1c) can sometimes be used to identify those who have diabetes or are at high
risk of developing diabetes. However in conditions where glucose values can change quickly (such as
pregnancy) or there are Hb or RBC abnormalities (haemoglobinopathies, haemolysis) the HbA1c value
might not accurately reflect glycaemic exposure and a GTT should be performed instead.
The Biochemistry Laboratory at SRFT offers a GTT service for out-patients on Monday and Friday mornings
at 09.15am, but usually only 2-3 patients can be accommodated at a time. Prior contact with the laboratory
on 0161 206 4961 is therefore essential to book a date. The laboratory will send out a confirmatory letter
(which gives details of the test and prior fasting required) directly to the patient; we will need details of the
patient’s home address and telephone number. All requests are vetted by the Duty Biochemist to ensure
that the patient does not already fulfil the criteria for D.M. on the basis of any past glucose results. Those
booking GTTs are advised to make contact with the laboratory when the patient is actually with them, as
this enables a suitable date to be arranged most easily.
It is important to note that there are no nursing staff or facilities in Pathology and therefore the patients
attending must not have special care needs.
Preparation of patient
The patient should continue with their normal diet (i.e. a normal intake of carbohydrate) for at least three
days prior to the test.
The patient must not have anything to eat or drink (other than plain water) after 10pm on the evening prior
to the test or on the day of the test, until it is completed. During the test, the patient should be at rest and
should NOT smoke.
Owing to diurnal variation of glucose tolerance, tests should be commenced between 9am and 10am.
Contraindications
This test should NOT be performed in patients who fulfil the criteria for diabetes mellitus. These are:
1)
a fasting plasma glucose >7.0 mmol/L on two or more occasions, or
2)
clinical symptoms of diabetes, e.g. polydipsia, polyuria, ketonuria and rapid weight loss with a
random plasma glucose >11.1 mmol/L.
Page 15 of 38
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This test should not be performed in patients who are under physical stress, e.g. post-surgery, trauma or
infection; or extreme psychological stress, as the catecholamine response will induce temporary
carbohydrate intolerance and may give misleading results.
Procedure
1 Check the patient’s fasting blood glucose using a point of care testing glucose meter.
If the result is ≥9 mmol/L, the test should be abandoned.
2 Take a 2ml blood specimen for plasma glucose (fluoride oxalate plasma - yellow top Sarstedt
Monovette). Fluoride oxalate tubes should be filled to the line and the blood mixed immediately with
the anticoagulant by gentle inversion of the tube. Label the tube clearly with the patient's full name,
date of birth and hospital number (if available), and the time and date of sampling, as for all subsequent
specimens.
3 Administer a 75g anhydrous glucose load in 200-300mL of water.
[N.B. The glucose preparations used may differ across SRFT and WWL (e.g. Glucosol (SRFT Pharmacy),
PolyCal, MaxiJul or Lucozade). Prepare the glucose preparation according to manufacturer’s instructions,
ensuring that the final volume is a maximum of 300mL and contains 75g anhydrous glucose].
The patient should consume the glucose load in its entirety within 5 minutes.
4 Take a further blood specimen for plasma glucose (fluoride oxalate plasma - yellow top Sarstedt
Monovette) exactly 2 hours after ingestion of the glucose load (ensure sample fully labelled and time of
sampling stated). Send the 2 blood specimens with an appropriately completed request form to the
laboratory.
5 The test is now complete and the patient should be given something to eat and drink before being sent
home.
Interpretation
MALES AND NON-PREGNANT FEMALES:
Normal Impaired
Impaired
Fasting
Glucose
Glycaemia Tolerance
Fasting <6.1
6.1-6.9
<7.0
And
And
And
2 hour <7.8
<7.8
7.8-11.0
Diabetes Mellitus
Diabetes
Mellitus
≥7.0
≥7.0
Or
And
≥11.1
≥11.1
Note: if at least one other abnormal
plasma glucose level on another
occasion, or HbA1c >48 mmol/mol,
then a diagnosis of DM can be made.
Adapted from WHO Guidelines 2006 and 2011.
Page 16 of 38
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PREGNANT FEMALES:
Normal Impaired
Gestational
Glucose
Diabetes
Tolerance of Mellitus
Pregnancy
Fasting <5.1
≥5.1
And
And/Or
2 hour <7.8
>7.8 & <8.5
≥8.5
Adapted from International Association of Diabetes and Pregnancy Study Groups (IADPSG)/ADA Guidelines
2013.
Notes
1 If the patient vomits, the test should be abandoned.
Send the fasting blood glucose sample to the laboratory with an explanatory note on the request form.
2 Pregnant patients diagnosed with gestational diabetes mellitus should be reassessed with a GTT 3
months post-partum.
3 Some drugs can affect GTT results, particularly glucocorticoids. Please state on the request form if the
patient is receiving any steroids.
References
World Health Organisation (2006) Definition and diagnosis of diabetes mellitus and intermediate
hyperglycaemia: report of a WHO/IDF consultation
World Health Organisation (2011) Use of glycated haemoglobin (HbA1c) in the diagnosis of diabetes
mellitus
NICE PH38 (2012) Preventing type 2 diabetes: risk identification and interventions for individuals at high
risk
American Diabetes Association (2013) Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 2013;
36(S1):S67-S74
Page 17 of 38
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Page 18 of 38
Mixed Meal Test for Investigation of Reactive Hypoglycaemia
Clinical Use
The Investigation of Reactive Hypoglycaemia.
The patient with a history suggestive of postprandial hypoglycaemia should undergo a mixed meal test.
That meal should include the components recognized by the patient as likely to cause hypoglycaemia and
should be conducted over 5 hours.
An oral glucose tolerance test should NEVER be used for the evaluation of suspected postprandial
hypoglycemia.
Preparation of Patient
This test should be performed as an inpatient test.
The patient should fast overnight. All non-essential medications should be withheld until the test is
completed.
Procedure
For a mixed meal diagnostic test, the patient consumes a meal that usually leads to symptoms and is then
observed for up to five hours.
1 Collect basal blood samples for glucose (fluoride oxalate tube – yellow top Sarstedt Monovette); serum
cortisol (serum gel tube – brown top Sarstedt Monovette), and insulin, proinsulin and C-peptide (serum
gel tube – brown top Sarstedt Monovette [SEPARATE SAMPLE]). Send all to lab immediately (to arrive at
laboratory within 60 minutes of collection).
2 Give the patient their mixed meal. The patient should consume the meal within 10-15 minutes.
3 Collect blood samples for glucose, and insulin, proinsulin & C-peptide at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 h
after giving the meal. The blood samples should reach the laboratory within 15 minutes of collection
4 Collect blood samples for glucose, cortisol, insulin, proinsulin and C-peptide at 5 h.
5 The patient should be closely observed throughout the test and any hypoglycaemic symptoms and their
time noted on the request form. (Instruct the patient to report if they feel unwell or symptomatic
during the test).
6 If it is judged necessary to treat before 5 hours because of severe symptoms, obtain samples for
glucose, (fluoride oxalate tube – yellow top Sarstedt Monovette); insulin, proinsulin, and C-peptide
(serum gel tube – brown top Sarstedt Monovette [SEPARATE SAMPLE]); cortisol and sulphonylureas
(serum gel tube – brown top Sarstedt Monovette) before administering carbohydrates.
Interpretation
A fall in venous plasma glucose to 2.5 mmol/L or less between 2-5 h post mixed meal together with
hypoglycaemic symptoms and a rise in serum cortisol of at least 220 nmol/L are consistent with, but no
proof of reactive hypoglycaemia. The rise in serum cortisol is considered essential for clinical significance to
be attached to the other findings.
Page 18 of 38
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Notes
1
No urine samples are required.
2
Smoking is not allowed throughout the test and only plain water is allowed.
Reference
Gama R et al., Clinical and laboratory investigation of adult spontaneous hypoglycaemia. J Clin Pathol 2003;
56:641-646.
Cryer PE et al., Evaluation and Management of Adult Hypoglycemic Disorders: An Endocrine Society Clinical
Practice Guideline. J Clin Endocrinol Metab 2009; 94:709-728
Page 19 of 38
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Page 20 of 38
Glycosade Loading Test
Clinical Use
To determine fasting tolerance in patients with Glycogen Storage Disease (GSD)
Preparation of Patient
DO NOT FAST prior to hospital attendance
Admit patient to MIU at 10.00am.
Procedure
1 Continue overnight feed until baseline bloods have been taken.
Measure BM on arrival.
2 Insert IV cannula. Once secure, insert a second IV cannula on other arm and administer 100 mL 0.9%
saline at 5 mL/hr to keep line patent. This second cannula is to be used should the first cannula fail.
Allow patient to rest for 20 minutes.
3 After 20 minutes rest, take baseline blood samples as detailed below.
DISCARD 1 FULL BROWN TOP TUBE BEFORE EACH HOURLY SAMPLING.
4 Weigh 100g Glycosade and mix with 200 mL water.
Give this orally, or via gastrostomy tube.
RECORD TIME OF ADMINISTRATION
If given via gastrostomy tube, flush with 50 mL water after administration.
5 Discontinue overnight feed.
Water can be consumed freely. No food / milk / sugar to be consumed for the duration of the test.
6 A jug of water, one sachet of S.O.S.25 and the blue beaker should be by the patient at all times.
7 Monitor BM and take bloods hourly as detailed below.
The test should take 8 hours, or less if the patient becomes hypoglycaemic. If the test is terminated early
please inform the duty biochemist (68212) or on-call BMS (bleep 3102) if after 5pm.
Baseline
1hr
2hr
3hr
4hr
5hr
6hr
7hr
8hr/completion
of test








Fluoride Glucose
Oxalate








(Yellow) Lactate
Lithium
Free Fatty








Heparin Acids (FFA)
(Orange)
B-Hydroxy








Butyrate
(B-OHB)

Serum
Creatine
(Brown) Kinase (CK)
Urate

Page 20 of 38
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8 At the end of the fast, give 1 sachet S.O.S.25 orally or via gastrostomy
9 Carbohydrate containing meal should be taken within 30 minutes otherwise severe hypoglycaemia may
develop.
10 If BM <3 mmol/L or if symptoms of hypoglycaemia develop, the fast should be discontinued, 1 sachet
S.O.S.25 should be given either orally or via the gastrostomy tube. Bloods as per “Completion of Test”
should be taken.
11 If the S.O.S.25 is not tolerated, commence 10% Glucose IV at 200 mL/hr
Consult Metabolic Consultant regarding discharge of patient.
For full protocol, please contact Dr Chris Hendricksz.
Page 21 of 38
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Growth Hormone Suppression Test (GTT with Growth Hormone)
The American Association of Clinical Endocrinologists have produced updated Guidelines regarding the
Diagnosis of Acromegaly which advocate the use of GTT for Growth Hormone Suppression as the Gold
Standard.
Indication
The investigation of gigantism or acromegaly
Preparation of Patient
The patient should be fasted for 10-16 hours and throughout the period of the test, but may drink plain
water. The patient should be at rest throughout the period of the test and smoking is not allowed.
Procedure
1
Check the patient’s fasting blood glucose using a point of care testing glucose meter.
If the result is ≥10 mmol/L, the test should be abandoned.
Take blood specimens and give glucose as detailed below. Yellow top (Fluoride oxalate) tubes should
be filled to the line and the blood mixed immediately with the anticoagulant by gentle inversion of the
tube. Label the tubes clearly with the patient's full name, date of birth and hospital number, and the
time and date of sampling, as for all subsequent specimens.
Time
0 Min
Glucose (fluoride oxalate plasma - Growth Hormone (Serum Gel tube –
yellow top Sarstedt Monovette)
brown top Sarstedt Monovette)
 (also request IGF-1 on this sample)

Give the appropriate glucose load prepared as follows:
Adults:
0 Min
30 Min
Glucose
Water
75 g
200 mL
1.25 g/kg
200 mL
(up to a maximum of 75g)
1.75 g/kg
Children aged 3-12:
200 mL
(up to a maximum of 75g)
The patient should drink this within a 5 minute period.
Give the patient a further 100 mL of water to drink following the glucose. Drink
within 5 minutes.


Children over 12:
60 Min


90 Min


120 Min


180 Min


Page 22 of 38
Clinical Biochemistry
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The test is now complete and the patient should be given something to eat and drink before being sent
home.
Interpretation of Results
Normal individuals respond by suppression of at least one GH level to <0.4 µg/L. In Acromegaly or
Gigantism serum GH concentration remains >0.4 µg/L and there is frequently a paradoxical rise in response
to hyperglycaemia.
Notes
a This test is not indicated as a diagnostic procedure in patients with a blood glucose >10 mmol/L after an
overnight fast.
The ingestion of 75 g glucose by a fasting diabetic patient may be dangerous.
b Patients occasionally vomit after ingestion of the glucose and the test is abandoned. This is not
necessarily a justification for abandoning the test, and continuation is often the simplest expedient,
provided an explanatory note is made on the request form accompanying the samples.
The interpretation of results may be sufficiently clear to avoid the repetition of the test on a future
occasion.
c
In addition to abnormal GH levels, carbohydrate intolerance is found in about 25% of acromegalic
patients.
Reference
Arafat AM et al., Growth Hormone Response during Oral Glucose Tolerance Test: The Impact of Assay
Method on the Estimation of Reference Values in Patients with Acromegaly and in Healthy Controls, and
the Role of Gender, Age, and Body Mass Index. J Clin Endocrinol Metab 2008; 93(4):1254-1262
Page 23 of 38
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Glucagon Stimulation Test
Indication
Assessment of growth hormone and ACTH reserve.
Contraindications
Malnourished patients who have not eaten for >48h.
Precautions
Patients may feel nauseous during and after the test (administration of intravenous anti-emetics can be
considered)
Late hypoglycaemia may occur (patients should be advised to eat small and frequent meals after the
completion of the test)
Preparation of Patient
The patient is fasted from midnight.
Procedure
1 At 8.30am cannulate the patient, and then allow the patient to rest on the bed for 30 minutes.
2
At 9.00 start the test.
Monitor pulse and BP every 30 minutes.
3
Take samples and give glucagon as follows:
Time
Glucose (yellow top Sarstedt Growth Hormone and Cortisol (Serum Gel
Monovette)
tube – brown top Sarstedt Monovette)
0 Min
0 Min
4


Give Glucagon 1 mg sub-cutaneously (1.5mg if patient >90kg)
OR Glucagon 15µg/kg
30 Min

60 Min

90 Min


120 Min


150 Min


180 Min


210 Min


240 Min


Send all the samples together to the Laboratory for Cortisol and Growth Hormone estimations.
Page 24 of 38
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Interpretation
Normal response: Growth Hormone >7 µg/L (males) or >10 µg/L (females) after 2 – 3 hours.
Peak cortisol should be >500 nmol/L.
In adults with growth hormone deficiency, peak growth hormone levels fail to rise above 3 µg/L.
Notes
Priming with sex steroids is recommended in prepubertal children who are over 10 years of age (either
chronological or bone age). Prescribe Stilboestrol 1mg 12 hourly for 48 hours prior to test.
This test must be performed at least 4 hours after any food and drink.
Reference
Molitch ME et al., Evaluation and Treatment of Adult Growth Hormone Deficiency: An Endocrine Society
Clinical Practice Guideline J Clin Endocrinol Metab 2011; 96:1587-1609
Yuen KCJ, Glucagon Stimulation Testing in Assessing for Adult Growth Hormone Deficiency: Current Status
and Future Perspectives. ICRN Endocrinology 2011, doi:10.5402/2011/608056
Barth JH, Pituitary Tests for Young Children, Leeds Pathology Biochemical Investigations in Laboratory
Medicine accessed 07.04.2014.
Page 25 of 38
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Page 26 of 38
Arginine Stimulation Test
Indication
Assessment of Growth Hormone reserve.
Note the Glucagon Stimulation Test is the preferred method for testing Growth Hormone reserve in adults.
Preparation of Patient
Fast the patient overnight.
Procedure
1
2
3
4
5
At 8.00am cannulate the patient in both arms, and then allow the patient to rest on the bed for 60
minutes.
At 9.00am start the test.
Monitor pulse and BP every 15 minutes.
Take samples and give Arginine as follows:
Time
Growth Hormone (Serum Gel tube –
brown top Sarstedt Monovette)
0 Min

0 Min
Give 30g Arginine in 100 mL 0.9% saline as
infusion over 30 minutes.
30 Min

60 Min

90 Min

120 Min

Send all the samples together to the Laboratory for Growth Hormone estimations.
Keep the patient lying down for an hour after the test, and check the patient's pulse and blood
pressure half-hourly and also before allowing them to get up.
Interpretation
If the plasma GH concentration peaks at ≥7 µg/L, further investigations are not indicated.
If the plasma GH concentration peaks at ≤3 µg/L, then a second alternative test of Growth Hormone
reserve may be necessary.
Reference
Alba-Roth J et al., Arginine Stimulates Growth Hormone Secretion by Suppressing Endogenous
Somatostatin Secretion. J Clin Endocrinol Metab 1988; 67:1186-1189
US National Library of Medicine Growth Hormone Stimulation Test accessed 07.04.2014.
Page 26 of 38
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Clonidine Stimulation Test
Indication
Assessment of Growth Hormone reserve.
Note the Glucagon Stimulation Test is the preferred method for testing Growth Hormone reserve in adults.
Preparation of Patient
Fast the patient overnight (4 hours for infants). Measure their height and weight and determine the surface
area from appropriate tables.
Procedure
1
At 8.30am cannulate the patient, then allow the patient to rest on the bed for 30 minutes.
2
At 9am start the test.
Monitor pulse and BP every 15 minutes.
3
Take samples and give Clonidine as follows:
Time
Glucose (yellow top Sarstedt Growth Hormone and Cortisol (Serum
Monovette)
Gel tube – brown top Sarstedt
Monovette)
0 Min
0 Min
4
5


ADULTS >18y: Give Clonidine 25 - 50 microgram i/v
CHILDREN <18y: Give Clonidine 0.15 mg/m2 body surface area i/v
30 Min

60 Min

90 Min


120 Min


150 Min


Send all the samples together to the Laboratory for Cortisol and Growth Hormone estimations.
Keep the patient lying down for an hour after the test, and check the patient's pulse and blood
pressure half-hourly and also before allowing them to get up.
Interpretation
If the plasma GH concentration peaks at ≥7 µg/L, further investigations are not indicated.
If the plasma GH concentration peaks at ≤3 µg/L, then a second alternative test of Growth Hormone
reserve may be necessary.
References
Gil'Ad et al., Oral Clonidine as a Growth Hormone Stimulation Test, Lancet 1979; 314:278-280
Page 27 of 38
Clinical Biochemistry
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Page 28 of 38
Lanes R and Hurtado E, Oral clonidine — an effective growth hormone-releasing agent in prepubertal
subjects, Journal of Pediatrics 1982; 100:710-714
Page 28 of 38
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Gut Hormone Profile
Clinical Use
Diagnosis of neuroendocrine tumours of the gastrointestinal tract.
Preparation of Patient
The patient should be fasted overnight. Proton pump inhibitors will lead to an elevation of some hormones
and should be stopped 2 weeks prior to the test (H2 blockers stopped at least 3 days prior to the test).
Procedure
1
Collect 3 x EDTA tube (red top Sarstedt Monovette).
2
Mix by gentle inversion.
3
Send the sample to the laboratory IMMEDIATELY. Please inform laboratory reception that these
samples are unstable and need immediate processing.
[Note: samples MUST be separated and frozen at -20°C within 15 minutes of venepuncture].
Interpretation of Results
The gut hormone profile consists of the following hormones (with attached normal adult ranges)
Vasointestinal Polypeptide (VIP)
<30
pmol/L
Pancreatic Polypeptide (PP)
<300 pmol/L
Gastrin
<40
pmol/L
Glucagon
<50
pmol/L
Somatostatin
<150 pmol/L
Chromagranin A
<60
pmol/L
Chromagranin B
<150 pmol/L
Reference
Supraregional Assay Service Handbook, www.sas-centre.org 2011.
Page 29 of 38
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48/72 hour Prolonged Supervised Fast (Insulinoma)
Indication
To demonstrate fasting hypoglycaemia if there is a suspicion of an insulinoma despite a normal overnight
plasma glucose level.
Preparation of patient
1 Admit patient to perform fast under close supervision with glucose (oral or i/v) available.
2 Admit ONLY to an endocrine ward (Langtree) (WWL) or MIU (SRFT).
3 Advise admit ONLY on a Monday or Tuesday before noon
4 Patients may drink plain water.
Procedure
1 Cannulate patient and continue/commence 48 hr fast.
2 Water is allowed. Patient should be active during waking hours but should not leave the ward.
3 Capillary blood glucose measurements should be done at regular (4 hr) intervals and whenever the
patient has symptoms suggestive of hypoglycaemia. Decrease to 1 hr intervals if the patient has glucose
<3.5 mmol/L.
4 Ketones should be suppressed with insulinoma even though patient is fasting because of the excess
insulin. Therefore urinary ketone testing (urine dipstick screen performed on ward) can give some
additional information.
Actions
When capillary blood glucose is <3.0 mmol/L or symptoms are convincing:
1
Bleep doctor urgently.
2
Take venous blood for urgent glucose (fluoride oxalate – yellow top Sarstedt Monovette), insulin and Cpeptide (serum sample – brown top Sarstedt Monovette). Send to biochemistry lab without delay to be
separated and frozen within 60 mins. Ring biochemistry up for an urgent glucose.
3
Take blood for sulphonylurea screen in a serum tube (serum gel tube – brown top Sarstedt Monovette).
4
Do not reverse hypoglycaemia until the lab confirms hypoglycaemia or unless the patient becomes
unconscious or fits.
5
Hypoglycaemia achieved if <2.2 mmol/L age under 60 or <2.5 mmol/L if over 60 years old. If achieved,
make sure the bloods have gone for insulin and C-Peptide and allow the patient to eat. They should not
go home until after a good carbohydrate meal.
6
If NOT hypoglycaemic then continue the fast.
7
If no symptoms have occurred at end of 48 hrs then take final samples for glucose, insulin and Cpeptide and sulphonylurea screen. In selected patients, the fast can be extended to 72 hours. [Samples
will only be despatched for analysis if hypoglycaemia is demonstrated]
Page 30 of 38
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Reference
Gama R et al., Clinical and laboratory investigation of adult spontaneous hypoglycaemia. J Clin Pathol 2003;
56:641-646
Page 31 of 38
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Luteinising Hormone Releasing Hormone (LHRH) or Gonadotrophin Releasing
Hormone (GnRH) Stimulation Test
Indication
Investigation of impaired hypothalamic or anterior pituitary function.
Please note these tests are NOT recommended by the RCOG or the RCP.
Preparation of Patient and Procedure
The patient does not require fasting. The test should preferably be carried out in the morning (8am –
10am).
1
Obtain a zero minute blood sample (5 mL) into a serum gel tube (brown top Sarstedt
Monovette).
2
Give 100 microgram of LH RH, i/v as a bolus.
3
Obtain further specimens for FSH and LH at 20 and 60 minutes.
Interpretation
In adult males the LH concentration rises 7- to 8-fold and FSH 2-fold above the basal levels. The peak
concentrations usually occur at 20 minutes. If the 60 minute value is greater than the 20 minute value, the
response is said to be delayed. The response in women is qualitatively similar but varies in magnitude with
the stage of the menstrual cycle and is dependent on circulating steroid concentrations particularly E2. The
LH response is 3- to 4-fold greater in the luteal phase than in the follicular phase with the greatest response
in the pre-ovulatory phase. The FSH responses are similar but less marked.
In children:
The LHRH test is often difficult to interpret and results should be interpreted alongside clinical findings
including full pubertal staging, testicular volume (boys) or ovarian ultrasound (girls). Puberty is a continuum
and so is the response to the GnRH test.
 Normal response: Increment of 3-4 IU/L of LH and 2-3 IU/L of FSH
 Pubertal LH level (>5 IU/L) and/or LH:FSH >1 are suggestive of gonadotrophin-dependent precocious
puberty
 Suppressed LH/FSH with high testosterone and oestradiol indicate gonadotrophin-independent
precocious puberty
 Increase in FSH level, without a rise in LH indicates the child is prepubertal
 Predominant FSH response in premature thelarche
 In premature adrenarche, values are prepubertal
Notes
a)
It should be established that both gonadal steroid and basal FSH/LH levels are low before embarking
upon this test.
b)
Response can be variable.
c)
If required, this test can be performed at the same time as the TRH test.
Page 32 of 38
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References
Practical Clinical Biochemistry. Ed. Gowenlock AH 6 Edition 1988 Redwood Burn
Menon PSN and Vijayakumar M, The Indian Journal of Paediatrics 2013 (Epub ahead of print)
Page 33 of 38
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Page 34 of 38
Short Synacthen Test (Addison’s Disease Screen)
Indication
For the Investigation of Adrenal Insufficiency. There is no evidence to support the use of this test in the
management of steroid replacement or withdrawal.
Preparation of patient
The patient is not required to fast but the test should be performed in the morning with the patient
recumbent. There is a slight risk of allergic reaction. The test should not be done within two weeks of
pituitary surgery.
Prednisolone, methylprednisolone and prednisone may all interfere in the Cortisol assay therefore the
patient should not take their steroid dose on the morning of the test.
Oestrogens [oral contraceptive pill (OCP) and hormone replacement therapy (HRT)] are known to increase
cortisol binding globulin (CBG) and thus may over-estimate cortisol levels. It is advised that OCP/HRT are
stopped 6 weeks prior to testing wherever possible.
Procedure
1
Take a basal sample of blood for serum cortisol (serum gel tube – brown top Sarstedt Monovette).
2
Inject i/m or i/v 250 microgram of tetracosactide (Synacthen).
3
Take a further blood sample for serum cortisol at 30 mins.
4
Send all the blood samples together, carefully labelled with the time of each sample, with the request
form to Biochemistry.
Caution
Do not delay starting therapy if adrenal failure is clinically suspected. If steroids are to be given as an
emergency treatment take a blood sample for serum cortisol (serum gel tube – brown top Sarstedt
Monovette) and ACTH (lithium heparin – orange top Sarstedt Monovette) IMMEDIATELY BEFORE
administration so that the diagnosis can be confirmed retrospectively. Once the short Synacthen test has
been performed it is unnecessary to withhold treatment in patients suspected of adrenocortical
insufficiency.
Interpretation
The interpretation of Short Synacthen Tests is method specific. At PAWS we currently utilise the Siemens
Cortisol method on the Siemens Advia Centaur XP. By this method, the test should be interpreted as
follows:
Basal cortisol
30 minute cortisol
Normal response
≥200 nmol/L
≥500 nmol/L
Equivocal response
350-500 nmol/L
Inadequate response
≤350 nmol/L
Reference
El-Farhan N et al., Clinical Endocrinology 2013; 78:673-680
Page 34 of 38
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Short Synacthen Test (Congenital Adrenal Hyperplasia)
Indication
For the diagnosis of congenital adrenal hyperplasia (CAH). It is often used in hyperandrogenised women to
diagnose late-onset CAH.
Preparation of patient
The patient is not required to fast but the test should be performed in the morning with the patient
recumbent. There is a slight risk of allergic reaction. The test should not be done within two weeks of
pituitary surgery.
Prednisolone, methylprednisolone and prednisone may all interfere in the Cortisol assay and, if possible,
the patient should not take their steroid dose on the morning of the test.
Oestrogens [oral contraceptive pill (OCP) and hormone replacement therapy (HRT)] are known to increase
cortisol binding globulin (CBG) and thus may over-estimate cortisol levels.
Procedure
1
Take a basal sample of blood for serum 17-hydroxyprogesterone (17-OHP) and serum cortisol (serum
gel tube – brown top Sarstedt Monovette).
2
Inject i/m or i/v 250 microgram of tetracosactide (Synacthen).
3
Take a further blood sample for serum 17-OHP and serum cortisol at 30 mins.
4
Send all the blood samples together, carefully labelled with the time of each sample, with the request
form to Biochemistry.
Interpretation
The interpretation of cortisol results in Short Synacthen Tests is method specific. See Short Synacthen Test
(Addison’s Disease Screen).
CAH is suggested by a baseline 17-OHP ≥10 nmol/L. A baseline of >100 nmol/L is diagnostic of homozygous
21-hydroxylase deficiency.
The ratio
Δ17𝑂𝐻𝑃
Δ𝐶𝑜𝑟𝑡
> 0.028 gives 70% diagnostic accuracy for heterozygote 21-hydroxylase deficiency, where
∆17𝑂𝐻𝑃 = 17𝑂𝐻𝑃30 − 17𝑂𝐻𝑃𝑏𝑎𝑠𝑎𝑙 and ∆𝐶𝑜𝑟𝑡 = 𝐶𝑜𝑟𝑡𝑖𝑠𝑜𝑙30 − 𝐶𝑜𝑟𝑡𝑖𝑠𝑜𝑙𝑏𝑎𝑠𝑎𝑙 .
Adults with rarer forms of CAH (e.g. 11-β-hydroxylase deficiency) have flat 17-OHP responses to synacthen.
Reference
El-Farhan N et al., Clinical Endocrinology 2013; 78:673-680
Kreutzmann DJ et al., Aust. Paediatr. J.1989; 25:340-345
Barth J et al., Biochemical Investigations in Laboratory Medicine, 2001 ACB Venture Publications
Page 35 of 38
Clinical Biochemistry
Dynamic Function Test Information for Users of the
PAWS Biochemistry Service
Pathology at Wigan and Salford
Q-Pulse Ref: BIO-I-P-011
Q -Pulse Revision
No: 3
Authorised By: Joanna Borzomato
Page 36 of 38
Thyrotropin Releasing Hormone (TRH) Stimulation Test
Indication
Investigation of anterior pituitary function. The development of TSH assays capable of accurate
measurements below 0.1 mU/L has obviated the need for the TRH test in most cases of thyroid practice
except perhaps in the differential diagnosis of TSHoma and thyroid hormone resistance (high TSH and high
thyroxine).
Preparation of Patient
The patient does not require fasting. The test should preferably be carried out in the morning (8am –
10am).
Procedure
1
Obtain a zero minute blood sample (5 mL) into a serum gel tube (brown top Sarstedt
Monovette).
2
Give 200 microgram of TRH i/v as a bolus. For children, 7 microgram/kg up to 200 microgram
maximum.
3
Obtain further specimens for TSH at 20 and 60 minutes.
Interpretation
In normal subjects TSH levels rise to between 5-25 mU/L at 20 minutes with an increment over the basal
value of at least 3 mU/L, thereafter decreasing slightly at 60 minutes.
In secondary hypothyroidism due to pituitary disease, basal TSH levels are low or low-normal and the TSH
response is impaired.
Notes
1 The use of this test is limited to the investigation of suspected secondary hypothyroidism.
2 Stress, psychological disturbances and drug therapy (including glucocorticoids) may impair the TSH
response and results must be interpreted accordingly
3 If required, this test can be performed at the same time as the LH RH test.
References
Barth J et al., Biochemical Investigations in Laboratory Medicine, 2001 ACB Venture Publications
Page 36 of 38
Clinical Biochemistry
Dynamic Function Test Information for Users of the
PAWS Biochemistry Service
Pathology at Wigan and Salford
Q-Pulse Ref: BIO-I-P-011
Q -Pulse Revision
No: 3
Authorised By: Joanna Borzomato
Page 37 of 38
Water Deprivation Test
Indication
To differentiate primary polydipsia, cranial diabetes insipidus (DI) and nephrogenic DI.
Preparation
Inform laboratory that test is being undertaken. Exclude adrenocortical or thyroid deficiency. Stop DDAVP
8h beforehand in patients already on treatment, but continue with anterior pituitary hormone
replacement. Fluid and food are allowed until 8am on the morning of the test.
Procedure
8am insert i/v cannula, weigh patient, patient empties bladder, measure urine volume and send for
osmolality. No fluids allowed throughout test. Measure BP, pulse, weight, urine and serum osmolality, and
urine volume hourly for 8 hrs (use table on page 38).
Proceed to DDAVP test if urine osmolality rises <30 mOsm/kg (in toto) over 3 successive urine samples.
STOP TEST if urinary osmolality ever >750 mOsmol/kg, serum osmolality >300 mOsmol/kg (give DDAVP 2
microgram i/v and fluids), weight loss >5% of baseline value (check serum osmolality), urine output exceeds
5 litres in absence of weight loss (suggests surreptitious drinking).
Interpretation
Post-dehydration osmolality Post DDAVP osmolality
(mOsm/kg)
(mOsm/kg)
Diagnosis
plasma
urine
urine
283-293
> 750
> 750
normal
> 293
< 300
< 300
nephrogenic diabetes insipidus
> 293
< 300
> 750
cranial diabetes insipidus
< 293
300-750
< 750
chronic polydipsia
< 293
300-750
< 750
partial nephrogenic DI or primary polydipsia
> 293
300-750
> 750
partial cranial DI
Submaximal urine concentration (500 – 700 mOsmol/kg) with no response to DDAVP (desmopressin)
suggests psychogenic polydipsia or partial nephrogenic DI.
Reference
SRFT Endocrinology Investigation Manual.
Thompson CJ. Polyuric states in man. Clin Endocrinol Metab 1989; 3:473-497
Miller M et al., Recognition of partial defects in antidiuretic hormone secretion. Ann Intern Med 1970;
73:721-729
Page 37 of 38
Clinical Biochemistry
Dynamic Function Test Information for Users of the
PAWS Biochemistry Service
Pathology at Wigan and Salford
Q-Pulse Ref: BIO-I-P-011
Q -Pulse Revision
No: 3
Authorised By: Joanna Borzomato
Page 38 of 38
WATER DEPRIVATION TEST
NAME:_______________________________
Hospital No.:__________________
Location:_________________
Date of Birth:__________________
Requesting Clinician:__________________
Weight
BP
U&Es
Serum
Osmolality
Urine
Osmolality
Urine
Volume
08:00
08:30
09:30
10:30
11:30
12:30
13:30
14:30
15:30
16:30
If urine osmolality remains <750 mOsmol/kg, give DDAVP 2 microgram i/m. Give free
fluids from now onwards.
17:30
18:30
19:30
20:30
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