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Effect of using 2 throat swabs vs 1 throat swab on detection of group A streptococcus by a rapid antigen detection
Elias N Ezike1, Chokechai Rongkavilit, Marilynn R Fairfax
1Carman and Ann Adams Department of Pediatrics, Division of Infectious Diseases, Children's Hospital of Michigan, 3901 Beaubien Boulevard, Detroit, MI 48201, USA.
Insights
Using two throat swabs does not improve the accuracy of the STREP A OIA MAX (OIA MAX) test for detecting group A streptococcus compared to using one swab. The test
Area of Science:
- Microbiology
- Infectious Diseases
- Diagnostic Testing
Background:
- Group A streptococcus (GAS) pharyngitis is a common bacterial infection.
- Rapid diagnostic tests are crucial for timely treatment and preventing complications.
- The STREP A OIA MAX (OIA MAX) test is a rapid method for GAS detection.
Purpose of the Study:
- To evaluate if using two throat swabs enhances the rapid detection of GAS by the OIA MAX test compared to using a single swab.
- To determine the sensitivity and specificity of the OIA MAX test with varying numbers of throat swabs.
Main Methods:
- A randomized study involving children aged 5-18 with acute pharyngitis.
- Group 1: One throat swab used for sheep blood agar culture and OIA MAX testing.
- Group 2: Two throat swabs collected simultaneously; one for culture and both for OIA MAX testing.
Main Results:
- No statistically significant difference in OIA MAX test sensitivity or specificity between using one (94.7% sensitivity, 100% specificity) and two swabs (92.4% sensitivity, 96.3% specificity).
- GAS was detected in 42.4% of 363 patients.
- OIA MAX test performance was not associated with pharyngitis severity (modified Centor criteria).
Conclusions:
- The OIA MAX test demonstrates comparable sensitivity and specificity regardless of whether one or two throat swabs are used.
- Employing two throat swabs does not improve the diagnostic accuracy of the OIA MAX test for GAS detection.
- The test's performance is not influenced by the clinical severity of pharyngitis.
Objective:
To assess the effect of using 2 throat swabs vs 1 on rapid detection of group A streptococcus by the STREP A OIA MAX (hereafter, OIA MAX) test.
Methods:
Children aged 5 to 18 years with acute pharyngitis were randomized to 1 of 2 study groups. In group 1, one throat swab was obtained, streaked first on sheep blood agar, and then used for OIA MAX testing. In group 2, two throat swabs were obtained simultaneously. One swab was streaked first on sheep blood agar and then joined with the other swab for OIA MAX testing. In both groups, the pledgets in the collection-transport tube were incubated in Todd-Hewitt broth. A positive group A streptococcus culture either by sheep blood agar or Todd-Hewitt broth was confirmed by a latex agglutination test.
Results:
Three hundred sixty-three patients were enrolled, 177 in group 1 and 186 in group 2. Cultures were positive for group A streptococcus in 154 (42.4%) of 363 patients. The sensitivity and specificity of OIA MAX testing were 94.7% and 100.0%, respectively, in group 1, and 92.4% and 96.3%, respectively, in group 2. There was no statistical difference between the sensitivity, the specificity, and the predictive values of the OIA MAX test performed with 1 swab compared with those performed with 2 swabs (P>.10). There was no association between OIA MAX test sensitivity and the severity of pharyngitis as measured by the modified Centor criterion (history of fever, absence of cough, presence of pharyngeal or tonsillar exudates, and presence of cervical lymphadenopathy) scores.
Conclusions:
The OIA MAX test yielded comparable sensitivity and specificity in both study groups. The use of 2 throat swabs instead of 1 swab did not increase the sensitivity of the OIA MAX test. The performance of the OIA MAX test did not depend on the severity of pharyngitis.
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