Semi-quantitative assessment of gastrointestinal viruses in stool samples with Seegene Allplex gastrointestinal panel assays: a solution to the interpretation problem of multiple pathogen detection?

Purpose The aim of the study was to determine and evaluate the clinical usefulness of pathogen specific semi-quantitative cut-offs in stool samples with multiple pathogen detections. Methods The PCR (Seegene Allplex Gastrointestinal Virus Assay) data from 4527 positive samples received over 16 months were retrospectively analyzed to investigate the distribution of the Ct values of each individual viral pathogen. By using interquartile ranges for each viral pathogen, pathogen specific semi-quantitative cut-offs were determined. Results After a thorough analysis of the Ct values, a well-founded decision to exclude all results with a Ct value higher than 35 was made. This approach made it possible to generate a more nuanced report and to facilitate clinical interpretation in case of mixed infections by linking a lower Ct value of a pathogen to a greater likelihood of being a relevant causative pathogen. Moreover, not reporting viral pathogens with a Ct value higher than 35 led to a significant reduction (p < 0.0001) of reported mixed infections compared to oversimplified qualitative or qualitative reporting. Conclusion By omitting very high Ct values and reporting semi-quantitatively, value was added to the syndromic reports, leading to an easier to read lab report, especially in mixed infections.