Group A beta hemolytic Streptococcus (GABHS) is commonly implicated in bacterial pharyngitis . Starting treatment with antibiotics for GABHS infection, within the first 24–48 hours of illness, when a bacterial cause is highly suspected, has been found to decrease duration of symptoms, such as sore throat, fever and adenopathy by approximately one day , and prevent complications of GABHS pharyngitis, particularly rheumatic fever and rheumatic heart disease . However, the majority of pharyngitis cases in adults are of viral etiology ; only 5–15% of cases suffer from bacterial pathogens that require prompt antibiotic treatment [5, 6].
The World Health Organization (WHO) defines an appropriate prescription as “administration of the right drug indicated for the disease, in the right dose, through an appropriate route of administration, for the right duration” . When these criteria are not fulfilled, the prescription is considered inappropriate. Inappropriate antibiotic prescriptions for treatment of pharyngitis have contributed to the emergence of resistant strains of oropharyngeal human flora  which in turn, have increased morbidity, mortality, and health-care costs . Approximately three quarters of pharyngitis patients have received inappropriate antibiotic prescriptions, by receiving antibiotics for viral infections or otherwise not adhering to the WHO definition [10–12].
First-line agents for treatment of bacterial pharyngitis include penicillin, ampicillin or amoxicillin.13 Alternative options include erythromycin (especially in patients with a non-life-threatening allergy to penicillin) and first-generation cephalosporins (CG) . Both erythromycin and cephalosporins are also considered reasonable alternatives to penicillin in patients who fail to respond to penicillin or continue to become re-infected following penicillin therapy [13–15]. As GABHS is the most important pathogen causing infection, fluoroquinolones, and sulfamethoxazole/trimethoprim that do not cover Gram-positive pathogens very well are not recommended. Although amoxicillin-clavulanate, clarithromycin, azithromycin and second-generation cephalosporins work very well against GABHS infection, they are considered third-line alternatives due to their broader spectrum of action and potential for causing resistance.
Throat swab and culture is the gold standard for diagnosis of pharyngitis. A rapid antigen detection test (RADT) can also give relatively specific diagnosis in a physician’s office. Although a WHO technical report states that there is less possibility of false-positive results with RADT, RADT kits vary in sensitivity, which ranges from 31–95%. Therefore, RADT cannot be substituted for standard blood agar cultures . Because antibiotics treatment should occur fairly promptly, diagnosis of pharyngitis is often based on clinical symptoms; throat swabs are not always taken . Thus to improve the diagnostic criteria, several scoring systems have been developed to predict, on a clinical basis, whether patients have bacterial or viral pharyngitis [17, 18].
Among the many devised clinical scores, the Centor criteria are reliable predictors of GABHS pharyngitis. They include evaluating patients for tonsillar exudates, tender anterior cervical lymphadenopathy or lymphadenitis, absence of cough, and history of fever (oral temperature greater than 38.3°C; 101°F) . More recently, the Centor score was modified by incorporating patient's age, which allows the physician to place patients in low-, moderate-, or high-risk groups. The use of the McIsaac Modified Centor score has helped in decreasing inappropriate antibiotic use by almost 88% .
Several guidelines have been published on diagnosis and treatment of streptococcal pharyngitis in adults; however, not all are in agreement. The American College of Physicians’ (ACP) guideline endorsed by Centre for Disease Control (CDC), American Academy of Family Physicians and the American Society of Internal Medicine, recommend that patients with low Centor scores of 0 or 1 (i.e., low risk for streptococcal pharyngitis) do not require any testing or treatment with antibiotics. For patients with Centor scores of 2 or, 3, the guidelines suggest using a RADT, which would give a sensitivity of > 80% for accurate diagnosis of GABHS infection, and prescribing antibiotics to patients with positive tests [20, 21]. Empirical treatment with antibiotics is recommended for patients with Centor scores of 3 or 4 . However, practice guidelines issued by the American Heart Association , American Academy of Pediatrics , and Infectious Diseases Society of America (IDSA)  recommend microbiologic confirmation by throat culture or RADT to diagnose all adults with pharyngitis prior to antibiotic prescribing, regardless of their Centor scores. IDSA and others are of the opinion that if prestigious organizations like AAFP and CDC endorse the option of not culturing at all for any given score, it would be unlikely that physicians would opt for either RADT or culture .
These concerns were addressed by McIsaac who pointed out that missed infections are not due solely to score approaches, as physicians do not obtain a throat swab for every case of sore throat . Therefore, treatment decisions based on clinical judgment would already miss 50% of GABHS infections, while 20–40% of the larger number of non-GABHS sore throat presentations would be identified as needing antibiotics [19, 28].
Given the controversy in clinical guidelines and not knowing how physicians in Pakistan generally treat their adult pharyngitis patients, we investigated whether antibiotics are prescribed appropriately for primary treatment of pharyngitis within a developing world setting and under low socio-economic conditions. We also evaluated the sensitivity and specificity of McIsaac Modified Centor scores in predicting GABHS pharyngitis in our patient populations. Finally, we evaluated whether the choice of antibiotic to treat pharyngitis was appropriate, in terms of antibiotic class, dose, and duration of therapy. Our study did not address use of antibiotics for secondary prevention of pharyngitis or asymptomatic carrier state.