Evaluation of an Innovative Rapid Diagnostic Test for Human Strongyloidiasis to Detect Specific IgG Antibody in Whole-Blood Samples

Human strongyloidiasis is an important intestinal parasitic disease that affects public health globally and is transmitted through contact with infective larvae on contaminated soil. Immunocompromised hosts can experience hyperinfection, which can lead to fatal systemic strongyloidiasis. Here, an innovative point-of-care (POC) test kit, the strongyloidiasis immunochromatographic blood test (the NIE-SsIR whole-blood ICT) kit is described. The kit was used to detect anti-Strongyloides IgG antibody in whole-blood samples (WBSs) instead of serum to diagnose strongyloidiasis. The kit is based on a mixture of two recombinant Strongyloides stercoralis protein antigens (NIE and SsIR) and colloidal-gold-labeled conjugates of anti-human IgG antibody to evaluate diagnostic values with simulated and fresh anticoagulated WBSs. The NIE-SsIR whole-blood ICT kit showed potentially high diagnostic values with simulated WBSs, obtained by spiking patients' sera with red blood cells. The sensitivity, specificity, and positive and negative predictive values were 93.0%, 93.7%, 88.6%, and 96.2%, respectively, at the prevalence of disease simulated under the laboratory conditions of 34.5%. In addition, 18 of 20 fresh anticoagulated WBSs from strongyloidiasis cases were positive, and all 15 WBSs from healthy volunteers were negative. The NIE-SsIR whole-blood ICT kit is a simple and convenient POC testing tool and can possibly be used with fingerstick blood samples, thereby not requiring the drawing of venous blood and separation of the serum. The NIE-SsIR whole-blood ICT kit can assist clinical diagnosis in remote areas and field settings without sophisticated equipment.