A urine-based assay for strongyloidiasis had a diagnostic accuracy comparable to the serological assay, and both performed better than traditional coprological assays, according to new data published in PLoS One.
A urine-based indirect enzyme-linked immunosorbent assay (ELISA) for detection of Strongyloides-specific immunoglobulin G (IgG) antibody that is comparable to serological tests has the advantage of being both noninvasive and easy to collect. A prospective cross-sectional study conducted from January to April 2010 in Kohn Kaen province, Thailand, recruited 149 individuals aged 22 to 86 years who submitted blood, urine, and fecal samples. The sample types were then used to compare diagnostic sensitivity and specificity of the urine-based test with current coprological and serological methods.
The urine-based test correlated well with the serological test and had a diagnostic sensitivity of 92.7% and a diagnostic specificity of 40.7%. The urine ELISA detection rate also surpassed the coprological method with a rate of 69% compared with 28%. The likelihood of positive strongyloidiasis diagnosis via the urine ELISA was directly related to increasing units of IgG detected in the sample. Investigators demonstrate higher sensitivity in urine and serum ELISA testing for strongyloidiasis compared with coprologic testing; the percentage positive for both the urine and serum ELISAs for strongyloidiasis were comparable (68.5% and 65.8%, respectively), whereas the percentage positive for strongyloidiasis by coprological examine was less than half (27.5%) of those for urine and serum tests.
Investigators noted that cross reactivity of the ELISA tests to other infections is possible, especially filariasis. However, the study area contains no reports of filariasis, and therefore the likelihood of cross-reactivity is low. Infections with Opisthorchis viverrini and Strongyloides stercoralis are frequent in the study area, and cross-reactivity with these species was anticipated.
The results of this study demonstrate that the urine assay is a promising alternative to blood samples for use in rapidly diagnosing strongyloidiasis, ahead of confirmation with standard diagnosis for clinical treatment. It may also be valuable for use in routine laboratory analyses and epidemiological surveillance, in addition to use as a diagnostic method in control programs. However, studies are still required to test the use of the urine assay on larger sample sizes and different endemic communities.
Eamudomkarn C, Sithithaworn P, Kamamia C, et al. Diagnostic performance of urinary IgG antibody detection: A novel approach for population screening of strongyloidiasis. PLoS One. 2018;13:e0192598