Pakistan Epidemiological Survey in Acute Pharyngitis

Pharyngitis is a common reason for patients' visit to doctors. Group A beta- hemolytic streptococci (GABHS) account for 15-30 percent of cases of acute pharyngitis in children and 5 to 20 percent in adults1.

Because the signs and symptoms of GABHS pharyngitis overlap extensively with other infectious causes, making a diagnosis based solely on clinical findings is difficult. In patients with acute febrile respiratory illness, physicians accurately differentiate bacterial from viral infections using only the history and physical findings about one half of the time.2 No single element of the patient's history or physical examination reliably confirms or excludes GABHS pharyngitis.3 Sore throat, fever with sudden onset (temperature greater than 100.4° F [38° C]), and exposure to Streptococcus within the preceding two weeks suggest GABHS infection. Cervical node lymphadenopathy and pharyngeal or tonsillar inflammation or exudates are common signs. Palatal petechiae and scarlatiniform rash are highly specific but uncommon; a swollen uvula is sometimes noted. Cough, coryza, conjunctivitis, and diarrhea are more common with viral pharyngitis.

The original Centor score uses four signs and symptoms to estimate the probability of acute streptococcal pharyngitis in adults with a sore throat.4 The score was later modified by adding age and validated in 600 adults and children.5,6 The cumulative score determines the likelihood of streptococcal pharyngitis.

Rapid Antigen Detection Tests (RADTs) have been developed for the identification of GABHS directly from throat swabs. Although these rapid tests are more expensive than blood agar culture, they provide results faster. Rapid identification and treatment of patients with streptococcal pharyngitis can reduce the risk of the spread of group A b-hemolytic streptococci, allowing the patient to return to school or work sooner, and can reduce the acute morbidity associated with the illness. The use of RADTs for certain populations (e.g., patients in emergency departments) has been shown to significantly increase the number of patients who are appropriately treated for streptococcal pharyngitis, compared with use of traditional throat cultures.7

The great majority of the RADTs that are currently available have an excellent specificity of 95%, compared with blood agar plate culture. This means that false-positive test results are unusual, and, therefore, therapeutic decisions can be made with confidence on the basis of a positive test result. Unfortunately, the sensitivity of most of these tests is 80%-90%, or even lower, compared with blood agar plate culture. It has been suggested that most of the false-negative RADT results occur for patients who are merely Streptococcus carriers and are not truly infected. However, early studies of first-generation RADTs demonstrated that a large proportion of patients with false-negative RADT results were truly infected with group A b-hemolytic streptococci and were not merely carriers.8