Development of immunochromatographic device as a point-of-care tool for serodiagnosis of human strongyloidiasis cases

Abstract

Human strongyloidiasis is an important gastrointestinal disease with an estimated 30 to 100 million people infected. Prevalence is generally underestimated since many infections are asymptomatic, and traditional diagnostic tests based on parasitological examination of stool samples are not adequately sensitive. Serological tests are useful and supportive but are still only available in a reference research setting. We made an immunochromatographic test (ICT) kit for rapid serodiagnosis of human strongyloidiasis. The antigen used in the ICT kit was extracted from larvae of Strongyloides stercoralis. Diagnostic efficacy of the kit was evaluated using human serum samples from strongyloidiasis patients, healthy persons, and those with other parasitoses. When using a cutoff level of 0.5 or above, the diagnostic sensitivity, specificity, and positive and negative predictive values at the prevalence of infection of 34.4%, were 93.3%, 83.7%, 76.7%, and 95.6%, respectively. This ICT kit is easy to use at the point-ofcare and a result can be obtained in 15 min. Sophisticated instruments and highly trained staff are not required. It can be used in several diagnostic and public-health settings, e.g., prevalence surveys in endemic areas, confirmation and monitoring of cure post-treatment, diagnosis and screening of infected but asymptomatic individuals, and populations "at risk" for hyperinfection syndrome or disseminated strongyloidiasis if they are given immunosuppressive treatment for other conditions.

Effectiveness of Strongyloides Recombinant IgG Immunoreactive Antigen in Detecting IgG and IgG4 Subclass Antibodies for Diagnosis of Human Strongyloidiasis Using Rapid Immunochromatographic Tests

“…Here, we developed two rSsIR-based ICT kits using S. stercoralis recombinant IgG immunoreactive antigen (GenBank: AAB97359.1) as the antigen for detecting IgG and IgG4 antibodies, making native antigens unnecessary in the mass production of the serodiagnostic assays. However, the sensitivities of both recombinant-based ICT kits were lower than the kit that use native antigen extracted from S. stercoralis larvae [24]. This is possibly owing to the variety and number sera used, incorrectly folded single rSsIR antigenic proteins, lack conformational epitopes, and variation in the duration of infection among the collected samples.…”

“…The ICT kit for diagnosis of human strongyloidiasis was recently developed based on IgG antibody detection in human sera against native antigen extracted from S. stercoralis larvae [24] The diagnostic sensitivity, specificity, positive predictive value, and negative predictive value are 93.3%, 83.8%, 76.7%, and 95.7%, respectively. This kit has been suggested as a POC test for the screening of asymptomatic Strongyloides carriers.…”

“…However, such methods are time-consuming and require specialized equipment not generally available at the point-of-care (POC) and often only found in advanced laboratories. Although a rapid diagnostic immunochromatographic test (ICT) has recently been developed as a POC tool using somatic S. stercoralis larval soluble extract antigen to detect IgG antibodies in human sera [24], the test uses a native antigen. This limits its practicality owing to limitations in the amount of material able to be extracted from parasites and the need to culture the parasites in a laboratory.…”

Evaluation of a Rapid IgG4 Lateral Flow Dipstick Test to Detect Strongyloides stercoralis Infection in Northeast Thailand

“…To date, there have been only three reports of the development of prototype lateral flow rapid tests for strongyloidiasis. [3][4][5] One of them, SsRapid TM , is an IgG4 dipstick test lined with S. stercoralis recombinant proteins. 5 The IgG4 level is significantly increased in individuals with chronic strongyloidiasis, and this level is higher in treatment-resistant patients.…”

“…The sensitivity rates were higher than that of the IgG4 cassette rapid test (78.3%) using the same recombinant protein. 3,4 Strongyloides IgG4 antibody levels are increased during chronic infection, whereas IgG is detected with both acute and chronic strongyloidiasis. 7 Therefore, it is not surprising that, generally, the infection prevalence detected by IgG is higher than that detected by IgG4.…”