Utility of rapid antigen detection test in group A ßhaemolytic streptococcal pharyngitis at a tertiary hospital, Gombe, North-East, Nigeria

Abstract

Background: Throat swab cultures still remain the gold standard for the confirmation of Group A Streptococcal (GAS) pharyngitis but Rapid Antigen detection Test (RADT) are increasingly becoming popular. Recent studies show RADT can be as sensitive and specific as the throat swab culture. This study aimed to determine the utility of RADT in the diagnosis of GAS pharyngitis in children at the Federal Teaching Hospital Gombe. Methods: A cross-sectional study that included 324 children aged 3- 18 years presenting with sorethroat at the out-patient department, consecutively recruited between April and September 2018. Socio-demographic and clinical findings were document. Throat swab samples were taken for RADT using Encode strep A Rapid antigen test and culture on 5% sheep blood agar. The sensitivity, specificity and positive and negative predictive values of the RADT was determined against throat swab cultures, which is the gold standard. Results: There were 190 (58.6%) females and Male to Female ratio of 1:1.4. The mean age was 8.3± 3.9 years. Only 125 (38.6%) of the participants were from low social class and 162 (62.3%) are from overcrowded households. Sociodemographic factors have no effect on the performance of the RADT, however, the use of antibiotics within 2 weeks prior to presentation significantly affected the performance of the RADT 1.4% (1/64) compared to 28.1% (73/260) for those without prior antibiotics use p<0.001. GAS was isolated in 73 (28.1%) of the children with pharyngitis. The RADT had sensitivity and specificity of 84.6% and 96.2% respectively and a PPV and NPV of 90.4% and 93.6% respectively. Conclusion: The RADT is reasonably sensitive and specific and can be used in the diagnosis of GAS pharyngitis in clinics as a substitute for throat swab cultures.

Keywords

• rapid test
• streptococcus
• pharyngitis