Download sore-throat-curriculum

Sore Throat
Jason Theiling, MD and Alison S. Clay, MD
2/10/2015
Objectives:
1) Identify Red Flags for Sore Throat
2) Propose a Differential Diagnosis for Sore throat, including key features for
various conditions
3) Use Clinical Decision Rules to determine who should receive testing for Strep
Throat
4) Suggest Treatment Options for patients with Sore Throat
Compare and contrast the following patient histories, identifying key signs for your
differential diagnosis: (note key findings are highlighted in yellow)
32 year old patient presents with sudden onset of sore throat, fever, and headache 2
days ago. He has also noticed some swollen lymph nodes and is feeling quite tired. He
does not have a cough.
65 year old patient with significant past medical history presents with a 3 month history
of hoarseness. The patient’s wife noticed a raspy voice a few months ago. He also
notes that he has cough, which he attributes to his smoking. He has no other real
complaints, except that he has noticed that his clothes are becoming a little loose.
45 year old patient presents with sudden onset of fever, ear pain, and sore throat on the
right side. The patient has also noticed some difficulty with swallowing and some
difficulty speaking.
What Diagnoses do you not want to miss? What are their key findings on history and
physical?
Condition
Signs and Symptoms
Epiglottitis
Severity out of proportion to exam
Drooling and or Inability to swallow
Muffled Voice/Inability to speak
Peritonsillar Abscess
Unilateral sore throat (1 point)
Hot potato voice (1 point)
Trismus (spasm of pterygoid muscles) (1 point)
Retropharyngeal Abscess
May have had penetrating trauma (1 point)
Difficulty swallowing or breathing (1 point)
Submandibular infection
Stiff Neck (1 point)
Drooling and or Inability to swallow (1 point)
Muffled Voice/Inability to speak (1 point)
Crepitus along jugular vein (1 point)
Cancer
Usually has a history of smoker
Chronic Duration
Hoarseness
Condition
Epiglottitis
Peritonsillar Abscess
Diagnostic testing/(FILMS OR EXAM)
Submandibular Abscess
(can also lead to
pulmonary abscess and
a clotted IJ vein)
“Lemierres Syndrome”
Retropharyngeal
Abscess
(remember the rule
7mm at C2 and 22mm
and C7)
What diseases mimic streptococcal infection and how?
Condition
(“Mononucleosis”)- caused
by RBV or CMV
Acute HIV
Pertussis
Gonorrhea or Chlamydia
Signs and Symptoms
Looks a lot like strep (have exudates just like strep)
May have exudate or may not
May have rash (classically after antibiotics given)
Enlarged spleen/Abd Pain—Make sure patient refrains
from contact activities for 6 weeks
May have leukopenia
Usually do not have exudate on tonsils
Often have painful ulcers in the mouth (look like canker
sores)
Fever, headaches, malaise, arthralgias
1/3 of patients have a gray membrane on posterior
pharynx, persistent cough
Usually asymptomatic
Make sure you take a sexual history (including oral sex for
women)
May have associated arthralgias or even septic arthritis
Frequency of various conditions:
Rational Exam
What to pay attention to in history and physical
History:
Physical:
Sexual history
Fever
Exposures to others with illness
Exudate on Tonsils
Presence of Cough
Cervical LAD
General health (weight loss)
Smoker
Testing and Testing:
Understanding testing threshold, pretest probability, sensitivity and specificity, Liklihood
Ratios and treatment threshold are key to understanding how/why we perform rapid
strep testing as well as perform culture.
Testing Threshold—what percentage of patients are you willing to send out your door
who may be positive, without further testing?
We set this number based on the severity of missing a diagnosis; for example, if a
condition is quite serious (heart attack or PE, we might set this number at 1%), for strep
throat, we might set this number higher, at 5%
Pretest Probability: This is how likely it is that you think a patient may have an illness.
This number is affected by disease prevalence. How does this number change in
different demographics or in different clinical settings?
 Demographics: In college students, the pretest probability of EBV may be 25 or
30%, but for a 65 year old, it might be 5%.
 Practice Settings: It may also be affected by where a patient presents—In
patients with chest pain, the pretest probability of a MI in the ED may be 10%,
while in the OP clinic, it may be 2%
Clinical decision rules can be used to set pretest probability, the ones used for strep
testing include the centor criteria
Centor Criteria for two patients
To understand how this decision rule also proposed a therapy, we need to consider
the Likelihood Ratios of a given test, our treatment threshold and Post test Probability
Treatment Threshold: how certain you have to be that a patient has a condition in order
to decide to treat. What affects treatment threshold?
 Costs of therapy (both in terms of risks to patients as well as financial costs)
 The potential benefit of therapy
 The risks of not treating. What are these for strep throat?
o Glomerulonephritis, myocarditis, retropharyngeal abscess, PANDAS,
rheumatic disease, etc. (HIGH RISKS)
 For example, guidelines for recommending statin therapies, suggest that the 10
year risk of MI exceed 7.5% over 10 years prior to recommending statins.
 For strep throat, since antibiotics are cheap and relatively safe, we might set this
number at 50%. The number is low because the risks of antibiotics are low and
the risk of missing and not treating GAHBS are high.
Now lets consider Test Characteristics:
Sensitivity-(True Positive)-Test will be positive if you have disease, but may have high
rate of false positives. (used for screening tests)
Specificity: (True Negative)- use for confirmatory testing. Test will be negative if you do
not have the disease
PPV: If the patient has a positive test, how likely the patient has disease (depends on
disease prevalence
NPV: if the patient has a negative test, how likely the patient does not have disease
(depends on disease prevalence)
+LR: how much the prosttest probability changes with a positive test (test characteristic)
-LR: how much the posttest probablity changes with a negative test (test characteristic)
For Rapid Strep Teseting
Sensitivity
Rapid Strep
Testing
65%
Specificity
(True
Negative)- use
for
confirmatory
testing. Test
will be negative
if you do not
have but may
give you false
negatives
97%
+ LR:
(characteristic
of test)
-LR ratio:
(characteristic
of test)
18
0.21
PPV (depend
on prevalence
of disease)
81%
NPV (depend
on prevalence
of disease)
93%
How to Apply EBM (Rational Clinical Exam, EBM Guide)
1) I set my testing threshold at 5%
2) Set my treatment threshold at 50%--the risk of antibiotics are low risk,
devastating if patient developed Rheumatic Heart Condition
3) I calculate my pretest probability for my two patients above
a. For one patient (see above) the Centor Criteria tell me to treat
empirically (I have exceeded my treatment threshold)
b. For the second patient, in whom my pretest probability was 30%. I use a
Fagan Nomogram to help me convert pretest probability to post test
probability using Liklihood Ratios.
i. A positive RADT gives me post test probability of 85%, higher than
my testing threshold, so I will treat
ii. However, a negative RADT gives me a post test probability of 7.5%
and that is still above my testing threshold, so I need the culture
to test further
Treatment for Strep Throat (from CDC and 2013 IDSA guidelines)
1) Amoxicillin 500mg-875mg BID for adults (depending on severity) x 10 days
2) Penicillin injection: 1.2 * 106 unites injected one time
3) Keflex is another alternative 500mg BID x 10 days
4) Second tier therapy for PCN allergic patients
a. Clindamycin 300mg TID 2 10 days
b. Azithromycin 500mg once daily for 5 days
Tips for Patients Receiving Abx (from CDC)
 Antibiotics increase the risk of resistance
 MUST TAKE ENTIRE DOSE, even though you feel better after 3-4 days; you are
still infectious for others, and you can “re-catch” the strep or have it recur if you
don’t complete all your medications
 Recommend patient specific symptomatic therapy –sprays with topical
anesthetics, ibuprofen and acetaminophen
Test for Cure/Relapses
 Consider Culture with testing for resistance if household contacts spread illness
among themselves!
 In households with proven GAHBS, you should perform a TEST OF CURE
 In patients with symptoms that do not resolve, consider household reservoirs, or
alterative diagnoses (HIV, EBV, Gonorrhea, Abscess formation, etc)
References:
AAFP
JAMA Rational Clinical Exam
CDC and IDSA treatment guidelines for GAHBS
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