Evaluation of a two-minute strep A direct swab test (SADST) on patients with pharyngitis at a primary care clinic.

A two-minute strep A direct swab test (SADST) was used to detect the presence of Lancefield group A streptococci (GAS) from the throats of 207 patients with pharyngitis at a primary-care clinic. The results were compared with a standard culture method. Fifty-one specimens were positive and 156 specimens were negative for GAS by culture. The SADST had a sensitivity of 96% (49 of 51) and specificity of 98.7% (154 of 156). The predictive values of a positive and negative SADST, for GAS, were 96% and 98.7% respectively. The SADST showed negative reactions with five specimens containing beta-haemolytic streptococci other than GAS and 34 known stock cultures other than GAS. Our results indicate that SADST is a rapid, simple, convenient and reliable test to use for diagnosis of GAS pharyngitis at primary care clinics, physicians' offices and clinical laboratories.