Download Overview of Clinical Chemistry

Overview of Clinical
Chemistry
Lecture 1
Definition
Clinical chemistry is the area of
pathology that is generally concerned
with analysis of bodily fluids.
 Also known as:

clinical biochemistry,
 chemical pathology,
 or medical biochemistry.
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Clinical chemistry 1
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Clinical chemistry is a science, a service, and an
industry.
As a science, clinical chemistry links the
knowledge of general chemistry, organic
chemistry, and biochemistry with an
understanding of human physiology.
As a service, the clinical chemistry laboratory
produces objective evidence from which medical
decisions may be made.
As an industry, clinical laboratories are
businesses which operate under the regulations
and practices that guide commerce
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Clinical chemistry 2
Clinical chemistry investigations are
used extensively in medicine for a variety
of purposes.
 The results of most clinical biochemical
investigations are expressed

quantitatively as a concentration,
 in the case of enzyme measurements, as an
activity.
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Purpose of Clinical Chemistry Tests
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Clinical chemistry 3
A central function of the clinical
chemistry laboratory is to provide
biochemical information for the
management of patients.
 Such information will be of value only if
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it is accurate and relevant,
 and if its significance is appreciated by the
clinician
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So that it can be used appropriately to
guide clinical decision-making.
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Common Clinical Chemistry Tests
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TEST
TEST
Sodium
Albumin
Potassium
Bilirubin
Chloride
Cholesterol
Glucose
Triglycerides
Urea (BUN)
Alkaline
Phosphatase
Creatinine
SGOT (AST)
Uric Acid
SGPT (ALT)
Inorganic Phosphate
Lactic
Dehydrogenase
(LDH)
Calcium
Creatine
Phosphokinase
(CPK)
The tests listed
are conducted
routinely by the
Chemistry Section
of the Clinical
Chemistry
Laboratory.
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Total Protein
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Types of Specimens for
Chemical Analysis

Whole blood, serum or plasma.

The most common specimen is
serum, collected in a tube with no
anticoagulant so that the blood will
clot.
Urine – often 24 hours collection
 Others – Cerebrospinal Spinal
Fluid (CSF) and other fluids
(Peritoneal Fluid, Amniotic Fluid)

CSF
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Synovial Fluid
Clinical chemistry Test Results
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Results from these tests provide valuable
clinical information about:
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whether specific tissue has been damaged,
and how severely,
and about the functional status of a variety of organ
systems.
Test results are interpreted with respect to
reference ranges, which are, most typically,
95% confidence intervals of values found in
clinically healthy populations.
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Clinical chemistry Test Results
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Biochemical tests are used in diagnosis, prognosis,
monitoring and Screening.
Biochemical marker analysis is one factor in the
assessment of the patient.
Physicians also gather
 history and symptoms of the complaint;
 examination findings, such as blood pressure;
 and testing by other health-care team members
in ancillary fields, such as radiology.
The physician uses all data to assess the patient
and implement a plan for treatment.
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Use of biochemical tests
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Screening
Biochemical tests are widely used to
determine whether a condition is present
sub-clinically.
 The best-known example is screening of
all newborn babies for phenylketonuria
(PKU), which is carried out in many
countries.
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Diagnosis
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Medical diagnosis is based on the patient's history, if
available, the clinical signs found on examination,
and on the results of investigations.
Investigations may be selected to help either confirm
or refute a diagnosis, and it is important that the
clinician appreciates how useful the chosen test is
for these purposes.
Making a diagnosis, even if incomplete, such as a
diagnosis of hypoglycaemia without knowing its
cause, may allow treatment to be initiated.
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Monitoring
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A major use of biochemical tests is to follow the
course of an illness and to monitor the effects of
treatment.
To do this, there must be a suitable analyte,
 for instance glycated haemoglobin in patients with
diabetes mellitus.
Biochemical tests can also be used to detect
complications of treatment,
 such as hypokalaemia during treatment with
diuretics,
 and are extensively used to screen for possible
drug toxicity, but also in some cases when a drug is
in use.
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Prognosis
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Tests used primarily for diagnosis may also
provide prognostic information and some are
used specifically for this purpose;
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for example, serial measurements of plasma
creatinine concentration in progressive renal disease
are used to indicate when dialysis may be required.
Tests can also indicate the risk of developing a
particular condition;

for example, the risk of coronary artery disease
increases with increasing plasma cholesterol
concentration.
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Categories of Biochemical Markers
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Biochemical markers are used for assessment
and diagnosis of disease:
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carbohydrates,
lipids,
proteins,
nucleic acids
and the derivatives of these markers.
The assessment of inorganic chemicals, provide
a measure of homeostasis in the body.
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such as ions,
minerals,
and dissolved gases,
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Categories of Biochemical Markers
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In addition to the measurement of these
endogenous substances, the clinical
chemistry laboratory provides
measurement of chemicals that are
exogenous to the body—
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beneficial chemicals,
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such as therapeutic drugs,
and harmful substances,
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such as poisons.
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Carbohydrates
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Carbohydrates are chemical substances that
contain only carbon, hydrogen, and oxygen.
 The simplest carbohydrates are
monosaccharides, which usually contain 3 to 6
carbons.
 Monosaccharides are the units that make up
more complex carbohydrates.
 Glucose, fructose, ribose, and galactose are
common monosaccharides of living
organisms.
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Carbohydrates as Biochemical Markers
of Disease
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The most common carbohydrate disorder in
humans is diabetes mellitus.
 This disease is caused by an inability to
produce or to respond to the hormone insulin.
 Laboratory tests of body fluids of individuals
with this disease show increased
concentrations of glucose.
 The laboratory tests for ketones, acids, and
glycosylated proteins provide measures of
disease severity.
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Lipids
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Lipids are, by definition, organic compounds
that are poorly soluble in solutions such as
water and soluble in organic solutions such as
ether.
 Only a limited number of lipids are clinically
important. This group includes
 fatty acids,
 triglycerides,
 cholesterol,
 and phospholipids.
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Lipids as Biochemical Markers of
Disease
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Clinical chemistry laboratories offer many tests
for lipid disorders. One of the most common
tests is the lipid profile.
 This panel of tests includes measures of
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triglycerides
cholesterol
Low density lipoprotein cholesterol (LDL-C)
and high-density lipoprotein cholesterol (HDL-C).
The results of testing for these lipids provide
measures of risk for coronary artery disease.
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Lipids as Biochemical Markers of
Disease
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Proteins and Amino Acids
The human body requires 20 amino
acids as the building blocks of proteins.
 Humans make some of these amino
acids but must gain the rest, as
essential nutrients, through the diet.
 Plants and bacteria produce the
essential amino acids and many others.
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Total Serum/Plasma Proteins and Plasma
Albumin as Biochemical Markers of Disease
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Plasma proteins have functions in many organ
and tissue systems.
They are
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carrier molecules,
receptor chemicals,
immune response agents,
and enzymes or catalytic proteins.
Total plasma protein is
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a measure of nutrition,
the status of many organs and tissues that are involved in
protein metabolism,
and the process of breakdown and excretion of protein
metabolites.
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Total Serum/Plasma Proteins and Plasma
Albumin as Biochemical Markers of Disease
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The measurement of plasma protein fractions
provides more specific evidence for diagnosis and
assessment of disorders.
Because of its importance in maintaining osmotic
pressure, the measure of albumin concentration is
a reflection of this pressure.
As a transport protein, the measurement of
albumin monitors the ability of the body to
transport such diverse substances as bilirubin,
fatty acids, and calcium through the blood.
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Enzymes
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An enzyme is a protein
catalyst that accelerates the
speed of a chemical reaction
by binding specifically to a
substrate, forming a complex.
This complex lowers the
activation energy in the
reaction without the enzyme
becoming consumed or
without changing the
equilibrium of the reaction.
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Enzymes as Biochemical Markers of
Disease
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Damage to tissue can release different types of
enzymes based on their location.
 For example, mild inflammation of the liver
reversibly increases the permeability of the cell
membrane and releases cytoplasmic enzymes such
as lactate dehydrogenase (LD), alkaline
phosphatase (ALP), and aspartate transaminase
(AST).
 Distribution of these enzymes within specific types
of hepatic tissues varies. ALP is more concentrated
in the biliary tree or canalicular tissues, while AST,
ALT, and LD are found in parenchymal hepatic
cells.
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The clinical chemistry laboratory and
organ systems
Cardiovascular Circulatory System
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The clinical chemistry laboratory offers analysis of
biochemicals for the assessment of
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acute myocardial infarction,
congestive heart failure
and coronary artery disease.
The laboratory offers measurement of lipids as
predictive factors for the development of heart
disease.
Measurement of arterial blood gases helps assess the
acid-base and oxygenation status of the patient.
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Respiratory Tract
The function of the respiratory tract is to
transfer gases from the environment to
tissue cells and from tissues cells to the
environment.
 The respiratory system also helps
maintain the acid-base balance in the
body.
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Respiratory Tract
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Measurement of arterial blood gases helps
assess the function of the respiratory system,
as well as the circulatory system.
 Blood oxygenation and pH are dependent
upon the uptake of oxygen by hemoglobin and
removal of carbon dioxide from red blood cells.
 The assessment of diseases such as chronic
obstructive pulmonary disease is dependent
upon the measurement of partial pressures of
oxygen and carbon dioxide in arterial blood to
monitor the function of the lungs.
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Liver
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The clinical chemistry laboratory offers a lot of
tests that provide information about specific
diseases of the liver.
 Measurement of the concentration of the
enzyme alanine transaminase (ALT) provides
information about hepatitis.
 Measurement of the enzyme alkaline
phosphatase (ALP) provides information about
biliary tract disorders.
 Analysis of the concentrations of proteins that
are made in the liver provides information
about the ability of the liver to perform this
function.
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Renal System
The clinical chemistry laboratory offers
many tests for different biochemical
markers of renal function, including
electrolytes, minerals, and protein
metabolic waste products.
 These biochemical markers are measured
in serum, urine, and other body fluids.
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Digestive System
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The clinical chemistry laboratory provides
information about nutritional status, intestinal
absorption, and function of the pancreas and
other organs of the digestive tract.
 The concentration of proteins of varying halflife helps establish the length of time of
nutritional deficiency.
 Analysis of gastric fluid assesses the ability of
the stomach to secrete acid.
 Measurement of serum concentrations of
lipase and amylase monitors the exocrine
function of the pancreas.
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Therapeutic drug monitoring
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Involves the analysis, assessment and
evaluation of circulating concentrations of
drugs in serum, plasma, or whole blood.
 Purpose is to ensure the medication dose is at
therapeutic range and not toxic.
 Medications dosage differ between each
patient based on metabolic process.
 Therapeutic range is narrow for some drugs
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below range: drug not effective
above rang: drug toxic
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Toxicology
Study of poisons.
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Clinical: the study of interrelationships
between toxin exposure and disease states.
(diagnosis & therapeutic intervention)
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Tumour Markers
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A tumour marker is a biological substance
synthesized and released by cancer cells or
substances produced by the host in response to
cancerous tissue.
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It may be used to:
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Detect the presence of a tumour
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Monitor the progress of disease
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Monitor the response to treatment
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