Development of an Immunochromatographic Test to Detect Antibodies in Simulated Whole-Blood Samples for the Diagnosis of Intestinal Capillariasis

Intestinal capillariasis is a zoonotic parasitic disease caused by Capillaria philippinensis, a fish-borne nematode. Patients present with clinical symptoms that include borborygmus chronic diarrhea, intermittent abdominal pain, weight loss, and several degrees of painless lower-leg edema. Atypical clinical manifestations and diagnostic confusion with diarrhea caused by gastrointestinal cancer, HIV infection, giardiasis, and hyperthyroidism may occur. Misdiagnosis and improper treatment can be fatal. Parasite eggs and larvae are passed intermittently in feces, rendering fecal examination insensitive. Serological methods can serve as a supportive diagnostic tool. In this study, we developed a simple and rapid antibody detection lateral-flow immunochromatographic test (ICT) as a point-of-care diagnostic tool. A new ICT format using a Trichinella spiralis larval extract antigen for antibody detection in simulated whole-blood samples (WBSs) was evaluated, and the results were compared with those obtained using serum samples. The sensitivity, specificity, and accuracy of IgG antibody detection in simulated WBSs were 100%, 94.3%, and 95.7%, whereas in serum samples, these values were 100%, 91.5%, and 93.5%, respectively. The results between simulated WBSs and serum samples did not differ significantly, with a concordance of 97.8%, yielding a Cohen's kappa of 0.95 (P <0.001). The ICT is easy to implement and can provide supportive diagnosis at the bedside or in local and remote hospitals with limited facilities.