ELISA for leptospiral 3-hydroxyacyl-CoA dehydrogenase in urine is a promising screening tool for acute leptospirosis

Introduction: Leptospirosis is a zoonotic disease that is prevalent worldwide. The leptospiral 3-hydroxyacyl-CoA dehydrogenase (3-HADH) is excreted in the urine of infected individuals. However, the potential use of 3-HADH as a biomarker for the diagnosis of leptospirosis using enzyme-linked immunosorbent assay (ELISA) has not been investigated. A technique that identifies Leptospira in a patient in urine sample will be valuable in regular diagnostics and epidemic scenarios, as opposed to existing serological approaches. This study aimed to develop and evaluate an ELISA that can detect 3-HADH in the urine of patients with confirmed acute leptospirosis and to assess its potential as a screening test for leptospirosis. Methods: Laboratory confirmation of acute leptospirosis was done by flaB-nested polymerase chain reaction (PCR) of plasma samples from suspected patients. ELISA-based determination of the presence of 3-HADH in the urine of PCR-positive patients versus PCR-negative patients matched for fever date was performed by coating ELISA plates with urine supernatants and using rabbit anti-3-HADH as the primary antibody. Receiver operating characteristic curve analysis was used to determine the cutoff values for the ELISA. The diagnostic measures between the PCR-positive and PCR-negative patients were compared using the Mann-Whitney U test. Results: In total 158 febrile patients were assessed, of whom 121 (76.6%) were male. Of the 15 flaB-nested PCR-positive patients, 12 were in the acute phase of the febrile illness. The best cutoff was an average optical density (ODav) value of 0.2200 for febrile patients. Sensitivity and specificity were 83.33% (95% confidence interval [CI], 51.59–97.91%) and 83.33% (95% CI, 76.05–89.13%), respectively. The ODav values for PCR-positive patients in the acute phase of the disease (≤7 days of fever) were significantly higher than those for PCR-negative patients (p<0.001, U=114.0, z= -4.946). Conclusion: Detection of 3-HADH in urine by ELISA appears promising for the screening of acute leptospirosis in suspected patients.