Evaluation of TestPack Strep A for Rapid Identification of Group A Streptococci.

The performance of a 10-minute immunoassay, TestPack Strep A, was compared with culture for the detection of Group A β-hemolytic streptococci (GABHS) from 298 throat swabs. When cultured, 17.4% of the samples grew GABHS. The values calculated for the test were sensitivity, 67.3%; specificity, 99.2%; positive predictive value, 94.6%; negative predictive value, 93.5%; positive likelihood ratio, 82.79; and negative likelihood ratio, 0.33. The sensitivity decreased with decreasing growth of GABHS in the culture. If cultures with only light GABHS growth were eliminated from the analysis, the sensitivity was increased to 74.4%. The test has the advantages of immediate results, available while the patient is still in the office; simplicity; easy-to-interpret end-points, high positive likelihood ratio; high specificity; and high predictive values, which make it a rather attractive supplement to sore throat management in a busy family practice. The cost of the kit, however, may diminish its attractiveness.