Acute Pharyngitis



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:

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).

Prevention of acute glomerulonephritis has never been demonstrated with antibiotic therapy.

Prevention of suppurative complications, such as peritonsillar abscess, is possible, although many patients do not present until an abscess has already developed.

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.

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