ACUTE PHARYNGITIS
Ali Vaezy, M.D.
WEEK 12: 03/21 – 03/25/05
Learning Objectives:
1. To understand the benefits and limitations of clinical scoring systems for the diagnosis
of streptococcal pharyngitis
2. To understand the natural history of streptococcal pharyngitis in adults and the
benefits (or lack thereof) of therapy
3. To learn how different professional groups (ACP/ASIM and ISDA) approach the use
of rapid antigen testing and throat culture
4. To reduce the rate of antibiotic prescriptions written for adults with sore throat
CASE ONE:
Mr. Soar Node is a 25-year-old man who presents to clinic for an urgent visit
complaining of sore throat and fever for two days. He has no other respiratory
symptoms. His past medical history is unremarkable. He takes no medications and has
no allergies. He is a mechanic and lives alone; he does not come into close contact with
children. On exam, his temperature is 101.6, and his other vital signs are normal. He
has tonsillar erythema with small amounts of white exudate and slightly enlarged,
tender, mobile anterior cervical lymph nodes. The remainder of his exam is normal.
Questions:
1. Does this patient require any further workup?
This is a question, which should inspire some debate among housestaff, as it has inspired
significant controversy in the literature. This patient has a classic presentation for
streptococcal pharyngitis, and he meets all four of the Centor criteria (temp >38 C;
absence of cough; swollen, tender anterior cervical nodes; tonsillar swelling or exudate).
According to the ACP/ASIM guidelines, this patient could either be tested with a rapid
antigen test or could be treated empirically for streptococcal pharyngitis. However, as
pointed out in part 2 of the ACP guidelines (p. 513), several studies of adults with
pharyngitis indicate that the presence of three or four of the Centor criteria has a positive
predictive value of only 40-60% for streptococcal infection. In one recent prospective
study (JAMA 2004; 291: 1587-1595), a score of 4 in an adult aged 18 or greater had only
30% positive predictive value. However, only 13 adults out of 333 had a score of 4.
The reason for this poor PPV has to do with the relatively nonspecific nature of the
symptoms of streptococcal pharyngitis; many studies have repeatedly demonstrated that it
is impossible to differentiate streptococcal pharyngitis from viral pharyngitis solely based
on clinical grounds. This patient could easily have viral pharyngitis caused by
respiratory viruses (adenovirus, RSV, rhinovirus, influenza, parainfluenza),
coxsackievirus, echovirus, CMV, or HSV. EBV is a common cause of pharyngitis in
adolescents and young adults. Other less common causes of pharyngitis include
Mycoplasma pneumoniae, Chlamydia pneumoniae, Arcanobacterium hemolyticum
(antibiotic therapy is not required for any of these, however). Neisseria gonorrheae is
one bacterial cause of pharyngitis in sexually active patients that would require treatment.
(Clin Infect Dis 2002; 35:113-125)
In sum, one could legitimately treat this patient empirically with antibiotics for presumed
streptococcal pharyngitis or perform a rapid antigen test. The first approach would result
in inappropriate antibiotic therapy about half the time—but only in the minority of adults
who meet all four Centor criteria. As pointed out in part 2 of the ACP guidelines (p.514),
the estimated antibiotic prescription rate would be 33% if patients with three or four
criteria were empirically treated—a vast improvement over the 75% rate currently
reported.
CASE ONE CONTINUED:
You decide to perform a rapid Streptococcal antigen test in clinic, which comes back
negative.
2. What do you do now?
If you follow the ACP/ASIM guidelines, you offer supportive care (analgesics and
antipyretics), and you do not send a swab for culture, if the sensitivity of your rapid
antigen test exceeds 80%.
At this point, undoubtedly some housestaff will say, “But what if you miss a case of strep
throat?” This would be an appropriate time to review the rationale and indications for
treatment of streptococcal pharyngitis in adults, nicely summarized on pp.511-512 of part
2 of the position paper:
a. Prevention of acute rheumatic fever, the time-honored major goal of therapy,
requires a number needed to treat of approximately 3000-4000 (in the absence of
an outbreak).
b. Prevention of acute glomerulonephritis has never been demonstrated with
antibiotic therapy.
c. Prevention of suppurative complications, such as peritonsillar abscess, is possible,
although many patients do not present until an abscess has already developed.
d. Prevention of spread of disease is an important consideration, especially in
children and institutionalized adults. In this patient, however, spread to others,
particularly children, is unlikely.
Finally, relief of symptoms is also a consideration, and antibiotic therapy, if instituted
within the first two to three days of symptoms, can reduce the duration of symptoms by
one to two days in patients with streptococcal pharyngitis.
In summary, the ACP guidelines would tell you to stop at this point, not do any further
testing, and not prescribe antibiotics. As explained above, the risk of not treating a
genuine streptococcal pharyngitis in this patient is extremely low.
However, the ACP guidelines would also have permitted you to prescribe antibiotics
without rapid antigen testing in the first place. The IDSA (Infectious Disease Society of
America) guidelines would not permit empiric antibiotics and would require you to
confirm a negative test with culture.
3. Why all the fuss about pharyngitis anyway?
Because roughly 75% of all adults with sore throats who who present to a physician
receive antibiotics, and many of them receive costly, broad spectrum antibiotics like
extended spectrum macrolides or quinolones. Only 5-15% of patients with pharnygitis
have strep throat. The potential for serious complications in these patients is quite low.
The ACP/ASIM and ISDA guidelines are designed, at least in part, to reduce the provision
of costly and unnecessary antibiotics to adults.
CASE TWO:
Ms. Farrah Gitis is a 34-year-old woman who presents to clinic complaining of sore
throat for one day. She also has had a mild nonproductive cough. Her PMH is
unremarkable. She takes occasional ibuprofen but is not otherwise on any medications,
and she has no allergies. She has two school-age children, both of whom were diagnosed
with strep throat last week and are currently on antibiotics. On exam, her temperature
is 100.9 and her other vitals are stable. She has erythematous tonsils without exudate
and mildly tender anterior cervical lymph nodes. The remainder of the exam is
unremarkable. Rapid streptococcal antigen test is positive.
4. How would you treat this patient?
As explained in part 2 of the ACP position paper, all of the evidence for prevention of
rheumatic fever was derived from studies involving administration of intramuscular
penicillin, and penicillin remains the drug of choice for non-allergic patients. A single
dose of 1.2 million units of benzathine penicillin IM is still the standard of care in many
parts of the world, although less commonly used in the US. Ten days of oral penicillin
VK, 500 mg BID or TID, is also an acceptable regimen. Amoxicillin may be administered
once daily, and thus may increase adherence. (It is important to realize that adherence to
antibiotics for 10 days is difficult to achieve, since most patients will have significant
improvement in their symptoms within the first two to three days of therapy.)
Penicillin remains the drug of choice because group A beta-hemolytic streptococcus
(GABHS) remains exquisitely susceptible to it. As cited on p.508 in part 1 of the
guideline, to date, there is no evidence of GABHS resistance to penicillin. Most labs, in
fact, do not routinely test GABHS for susceptibility.
5. How would you treat this patient if she reported a history of rash with penicillin?
You could use a first-generation cephalosporin, since only 10-15% of penicillin-allergic
patients will have a reaction to cephalosporins. If the patient had anaphylaxis or other
serious allergic reaction, you could use erythromycin.
Obviously, there are many other antibiotics that are effective against GABHS
(clindamycin, second and third generation cephalosporins, other macrolides like
azithromycin), but most of these have a much broader spectrum of activity and also cost
much more than penicillin.
CASE THREE:
Ms. Rina Rhea is a 53-year-old woman who is your regular patient in clinic. She comes
in for an urgent visit because her 6-year-old grandson has strep throat, and she wants to
get tested. Her only symptom is rhinorrhea. Her PMH is significant for hypertension,
for which she is on HCTZ. Her exam is unremarkable.
6. Would you do a rapid strep test on this patient?
Absolutely not. This patient has no Centor criteria and thus has less than 10% chance of
having GABHS. In addition, she is in an age group in which GABHS pharyngitis is rare,
and in which serious sequelae are extremely rare. Finally, a positive rapid antigen test in
this patient would not indicate disease but, if anything, a carrier state that would not
require treatment. There is no indication to do a rapid antigen test or throat culture in
this patient.
CASE FOUR:
Mr. Lee Node is a 21-year-old man who presents to clinic complaining of fever, sore
throat, headache, and myalgias for three days. His PMH is not significant, and he is not
on any meds. His exam is notable for temperature of 102.4, mildly erythematous
oropharynx without exudate, diffuse lymphadenopathy (anterior and posterior cervical,
axillary, and inguinal), and a non-pruritic erythematous maculopapular rash on his
abdomen and back.
7. Would you do a rapid strep test on this patient?
No. This patient’s presentation is of a flu-like illness with diffuse lymphadenopathy and
nonspecific rash. The differential diagnosis for this is broad but would not include
streptococcal pharyngitis. On further questioning, Mr. Node revealed that he had
engaged in unprotected receptive anal intercourse with a man two weeks earlier. His
illness turned out to be acute HIV infection.
References:
1. Snow V. et al. Principles of appropriate antibiotic use for acute pharyngitis in
adults. Ann Int Med. 2001; 134: 506-508.
2. Cooper R.J. et al. Principles of appropriate antibiotic use for acute pharyngitis in
adults: background. Ann Int Med. 2001; 134: 509-517.
Additional References:
1. Bisno A.L. et al. Practice guidelines for the diagnosis and management of group A
streptococcal pharyngitis. Clin Infect Dis. 2002; 35:113-125.
2. McIsaac W.J. et al. Empirical validation of guidelines for the management of
pharyngitis in children and adults. JAMA. 2004; 291: 1587-1595.