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Abstract
Background
Throat culture is the golden standard for diagnosis of group A streptococcal (GAS) pharyngitis. However, because it is a time-consuming procedure, antibiotics are often empirically administrated. Rapid antigen tests (RATs) can detect bacterial infections within 15 minutes, thus helping to reduce unnecessary administration of antibiotics.
Methods
In total, 108 patients, between 3 and 17 yr of age, who visited our hospital from August 2011 to July 2012, were tested for suspected acute pharyngitis with two RATs––SD Bioline Strep A (SD, Korea) and BinaxNOW Strep A (Binax, Inc., USA)––as well as throat culture. We compared the sensitivity, specificity, and consistency of the two RATs and assessed the clinical manifestations of GAS pharyngitis.
Results
Of the 108 patients, 15 were confirmed to have GAS pharyngitis by throat culture. The SD test showed a sensitivity of 93.3% and a specificity of 97.8%; the positive and negative predictive values were 87.5% and 98.9%, respectively. The Binax test showed a sensitivity of 86.7% and a specificity of 100%; the positive and negative predictive values were 100% and 97.9%, respectively. The Kappa values for conformity degree were high, 0.887 and 0.918 in the SD and the Binax tests, respectively (P=0.00). Clinical manifestation assessment of GAS pharyngitis indicated that scarlatiniform rash and strawberry tongue were significantly associated signs (P<0.05).
Figures and Tables
Table 1
Symptoms and signs of acute pharyngitis
Table 2
Comparison of rapid antigen detection test results based on the number of colonies of group A streptococcus in throat culture
| Number of colonies | Number of children | Positive cases of SD Bioline Strep A | Positive cases of BinaxNOW Strep A |
|---|---|---|---|
| No growth or rare | 93 | 2 | 0 |
| Moderate | 11 | 10 | 9 |
| Many | 4 | 4 | 4 |
| Total | 108 | 16 | 13 |
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