Performance Comparison of In-House and Commercial Biosynex Helmints AMPLIQUICK® Real-Time PCR Assays for the Diagnosis of Schistosoma mansoni and Strongyloides stercoralis in Stool Samples.

Background/

Objectives

The timely diagnosis of schistosomiasis and strongyloidiasis is important because of their potentially severe, even lethal, consequences. European diagnostic laboratories must comply with the European In Vitro Diagnostic (IVD) Regulation, which requires justifying the use of in-house assays when CE-IVD-marked kits are available. We aimed to compare the performance of the Biosynex Helminths AMPLIQUICK® RT-PCR and the multiplex in-house RT-PCR for the diagnosis of Schistosoma mansoni and Strongyloides stercoralis currently used in our department, an Italian reference centre for tropical diseases.

Methods

We conducted a performance comparison study on biobanked frozen stool samples classified as cases or controls according to PCR and/or copromicroscopy at diagnosis. Both RT-PCRs were performed on DNA re-extracted from the same stool aliquot. Sensitivity and specificity were compared using McNemar's Chi-squared test, while agreement was assessed using Gwet's AC1 and Cohen's K coefficients, and Bland-Altman analysis.

Results

A total of 45 S. mansoni cases with 52 controls and 29 S. stercoralis cases with 54 controls were analyzed. For both S. mansoni and S. stercoralis, sensitivity and specificity were not significantly different between RT-PCRs (p = 1). Concordance was perfect for controls (AC1 = 1) in both cohorts, but was poor for S. mansoni cases (AC1 = 0.38) and good for S. stercoralis cases (AC1 = 0.78).

Conclusions

Performance was not significantly different between in-house and Biosynex RT-PCRs. Nevertheless, careful assessment of the specific molecular targets included in the panels and prospective evaluation of any newly introduced tests should be implemented to minimize the impact of clinically significant discrepancies.