Utility of the loop-mediated isothermal amplification assay for the diagnosis of visceral leishmaniasis from blood samples in Ethiopia

Abstract

Rapid and accurate diagnosis of visceral leishmaniasis (VL) is needed to initiate prompt treatment to reduce morbidity and mortality. Here, we evaluated the performance of loop-mediated isothermal amplification (LAMP) assay for the diagnosis of VL from blood in an endemic area in Ethiopia. LAMP was positive in 117/122 confirmed VL cases and negative in 149/152 controls, resulting in a sensitivity of 95.9% (95% CI: 90.69-98.66) and a specificity of 98.0% (95% CI: 94.34-99.59), respectively. The sensitivity of the LAMP assay was 95.0% (95% CI: 88.61-98.34) in HIV-negatives and 100% (95% CI: 85.18-100.0) in HIV-positives. Compared with microscopy, LAMP detected 82/87 (94.3%, 95% CI: 87.10-98.11) of the microscopy1 cases and was negative in 11/27 (40.7%, 95% CI: 22.39-61.20) of the microscopy2 cases. Compared with the rK39 serology, LAMP detected 113/120 (94.2%, 95% CI: 88.35-97.62) of the rK391 cases and was negative in 149/154 (96.8%, 95% CI: 92.59-98.94) of the rK392 cases. However, when compared with microscopy only, rK39 detected 83/87 (95.4%, 95% CI: 88.64-98.73) of the microscopy1 cases and negative in only 12/27 (44.4%, 95% CI: 25.48-64.67) of the microscopy- cases. There was an excellent agreement between rK39 and LAMP (Kappa 5 0.91, 95% CI: 0.86-0.96). Furthermore, an algorithm using rK39 followed by LAMP would yield a sensitivity of 99.2% (95%CI: 95.52-99.89) and a specificity of 98.0% (95% CI: 94.34-99.59). The findings demonstrate that LAMP assay is an accurate and rapid molecular assay for VL diagnosis, including in HIV-1 coinfected patients, in an endemic setting.