Evaluation of the Strongyloides stercoralis VirClia IgG monotest for the diagnosis of strongyloidiasis in a diverse clinical cohort

ABSTRACT Strongyloides stercoralis is an intestinal nematode with the capacity for lifelong autoinfection and potentially fatal hyperinfection in immunocompromised patients. In non-or-low-endemic settings, serology is central to diagnosis, but most current assays are batch-dependent, labor-intensive, and restricted to referral centers. There is an unmet need for a rapid, robust, random-access screening test. To evaluate the clinical and diagnostic performance of the Strongyloides VirClia IgG monotest, a CE-IVD chemiluminescent immunoassay (Vircell), in a non-endemic setting, we tested stored sera from microbiologically confirmed strongyloidiasis cases, external quality assessment samples, healthy controls, and a broad disease-control panel covering viral, bacterial, protozoal, and other helminth infections. All samples were tested on the VirClia Lotus analyzer and compared with a previously published in-house enzyme-linked immunosorbent assay. A total of 69 confirmed cases and 210 controls (171 disease controls, 39 healthy controls) were analyzed. Sensitivity was 98.6% (68/69; 95% confidence interval [CI] 92.2%–99.7%), and specificity was 98.1% (206/210; 95% CI 95.2%–99.3%). The area under the receiver operating characteristic curve was 0.985 (95% CI 0.961–1.000), with a high positive (LR+ = 52) and near-perfect negative (LR− = 0.015) likelihood ratio. All four false positives occurred in patients with concurrent parasitic infections; cross-reactivity was otherwise only sporadic. Inter-laboratory comparison showed comparable results. The Strongyloides VirClia IgG monotest showed excellent diagnostic accuracy in a diverse, clinically relevant cohort. Combined with its random-access format and short turnaround time, the assay is well suited as a first-line screening tool for strongyloidiasis in non-endemic settings. IMPORTANCE Strongyloides stercoralis is an intestinal roundworm with a substantial global disease burden. Infection is typically chronic and largely asymptomatic, but in severely immunocompromised patients—such as those on immunosuppressive therapy or with hematological malignancies—it can progress to a hyperinfection syndrome, carrying a high risk of complications and mortality. As immunosuppressant use rises and treatment options for hematological malignancies expand, the at-risk population for Strongyloides hyperinfection syndrome continues to grow. Medical microbiological laboratories therefore need a reliable and sensitive strongyloidiasis screening assay with a short turnaround time. In this study, we show that the S. stercoralis VirClia IgG monotest can meet this need, with high diagnostic accuracy in a relevant and diverse clinical cohort. These findings support adoption by other laboratories after local verification, without the need for an extensive in-house validation as presented here.