Comparison of two commercial and one in-house real-time PCR assays for the diagnosis of bacterial gastroenteritis.

Introduction: The aim of the study was a comparative evaluation of in-house real-time PCR and commercial real-time PCR (Fast Track Diagnostics (FTD), ampliCube/Mikrogen) targeting enteropathogenic bacteria from stool in preparation of Regulation (EU) 2017/746 on in vitro diagnostic medical devices.

Methods: Both 241 stool samples from patients and 100 samples from German laboratory control schemes ("Ringversuche") were used to comparatively assess in-house real-time PCR, the FTD bacterial gastroenteritis kit, and the ampliCube gastrointestinal bacterial panels 1&2 either with the in-house PCRs as gold standard and as a test comparison without gold standard applying latent class analysis. Sensitivity, specificity, intra- and inter-assay variation and Cohen's kappa were assessed.

Results: In comparison with the gold standard, sensitivity was 75-100% for strongly positive samples, 20-100% for weakly positive samples, and specificity ranged from 96 to 100%. Latent class analysis suggested that sensitivity ranges from 81.2 to 100% and specificity from 58.5 to 100%. Cohen's kappa varied between moderate and nearly perfect agreement, intra- and inter-assay variation was 1-3 to 1-4 Ct values.

Conclusion: Acceptable agreement and performance characteristics suggested replaceability of the in-house PCR assays by the commercial approaches.