Optimizing the diagnosis of pediatric group a streptococcus (GAS) pharyngitis: A comparative analysis of rapid...

Group A Streptococcus (GAS) is a common cause of acute pharyngitis in children. Accurate and timely diagnosis is essential to guide appropriate antibiotic use and minimize unnecessary prescribing. While bacterial culture remains the gold standard, rapid antigen detection tests (RADTs) and molecular tests are increasingly implemented. A total of 100 throat swabs were prospectively collected from pediatric patients with suspected GAS pharyngitis. Each sample underwent bacterial culture, RADT, and a molecular test. Sensitivity and specificity of RADT and the molecular test were calculated using culture as the reference. In addition, culture and RADT were also evaluated using the molecular test as the reference standard. In parallel, recommendations from European, North American, and Belgian guidelines were reviewed. When compared to bacterial culture, OSOM® Strep A Test demonstrated a sensitivity of 91% [73-97] and a specificity of 100% [95-100], while ID NOW™ Strep A 2 showed a sensitivity of 87% [67-95] and a specificity of 94% [85-97]. When the molecular test was used as the reference, both bacterial culture and OSOM® Strep A Test exhibited similar sensitivities (83% [64-93] and 80% [60-91], respectively), with high specificities (96% [89-98] and 99% [92-99]). Guideline analysis revealed different approaches to GAS diagnosis, varying in reliance on clinical scores, various routine testing, or confirmatory culture. At the Laboratoire Hospitalier Universitaire de Bruxelles - Universitair Laboratorium Brussel (LHUB-ULB), a rapid antigen detection test is used as the first-line diagnostic tool, with bacterial culture performed for confirmation. Implementation of ID NOW™ Strep A 2 is not currently planned, given its practical and analytical limitations as well as cost considerations. However, as molecular diagnostics advance, bacterial culture is increasingly seen as an imperfect reference, underscoring the need for alternative frameworks to evaluate emerging tests.