Molecular Diagnostics for Group A Streptococcal Pharyngitis: Clinical and Economic Benefits in the Belgian Healthcare Context.

(1) Background: Group A Streptococcal (GAS) pharyngitis is common, resulting in numerous ambulatory visits. Accurate diagnosis is challenging. This study evaluated the clinical utility, cost, and performance of a nucleic acid amplification test (NAAT) for GAS detection, comparing it to a rapid antigen detection test (RADT) and throat culture. Additionally, we assessed the diagnostic stewardship related to these testing methods to ensure appropriate antibiotic use in clinical practice.

Methods: Between November 2022 and February 2023, 82 throat swabs were analyzed, with McIsaac clinical scores calculated for each. The Abbott ID NOW STREP A 2 NAAT and Sekisui Diagnostics' OSOM^® STREP A RADT were performed, followed by bacterial culture. Diagnostic performance was compared using culture as the gold standard.

Results: Of the 82 samples, 28 (34.14%) tested positive for pathogenic germs, primarily Streptococcus pyogenes (92.85%). RADTs showed a sensitivity of 80.76% and a specificity of 100%, while NAATs demonstrated a sensitivity of 100% and specificity of 96.42%. Cost analysis indicated the need for reimbursement adjustments to optimize NAAT's economic benefits. Clinical data indicated that symptoms alone were insufficient for reliable diagnosis.

Conclusions: This study confirmed the superior sensitivity of Abbott's Strep A2 NAAT over RADT. Given the Belgian guidelines against routine antibiotic treatment for pharyngitis and considering local treatment recommendations and cost, implementing NAAT for GAS detection in Belgian laboratories is less beneficial. However, the role of NAAT in supporting antimicrobial stewardship by ensuring appropriate antibiotic use remains significant.