Evaluating clinical decision rules and rapid diagnostic tests for the diagnosis of Streptococcus pyogenes pharyngitis in Gambian children: a diagnostic accuracy study.

OBJECTIVES

Accurate diagnosis of Streptococcus pyogenes (S. pyogenes) pharyngitis is imperative in high rheumatic heart disease-burden countries. We aimed to assess the diagnostic accuracy of two rapid diagnostic tests and five clinical decision rules (CDRs) in The Gambia.

METHODS

Children under 16 years presenting with signs and symptoms of pharyngitis were recruited at Sukuta Health Centre, The Gambia. A rapid antigen detection test (SD Bioline; LFT) and a rapid gene-amplification test (ID NOW™ STREP A2) were assessed for diagnostic accuracy alongside five CDRs against culture and qPCR for S. pyogenes. Logistic regression was used to determine risk factors for S. pyogenes pharyngitis.

RESULTS

Among 376 participants, S. pyogenes positivity was 9·8% (37/376) by culture, 32·4% (122/376) by PCR, 31·6% (119/376) by LFT, and 33·3% (122/366) by ID NOW. The ID NOW had sensitivities and specificities of 94·6% and 73·6% against culture, and 93·5% and 87·6% against PCR. The LFT had sensitivities and specificities of 83·8% and 74·0% against culture and 55·7% and 80·0% against PCR. The Smeesters CDR performed best with an area under the curve (AUC) of 0·694 against culture. S. pyogenes pharyngitis risk increased with age. Recent chest infection/cough (aOR 1·89, 1·08-3·28) and concurrent skin infection (aOR 2·11, 1·21-3·69) were associated with increased S. pyogenes pharyngitis.

CONCLUSIONS

The LFT and the CDRs had poor performance in detecting S. pyogenes pharyngitis compared to PCR and culture. Molecular methods detected a higher proportion of S. pyogenes than culture. Affordable and sensitive diagnostics are urgently needed to improve S. pyogenes management in resource-limited settings.