3 years ago

A comparison of two molecular methods for diagnosing leptospirosis from three different sample types in patients presenting with fever in Laos

To compare two molecular assays (rrs qPCR vs. a combined 16SrRNA and LipL32 qPCR) on different sample types for diagnosing leptospirosis in febrile patients presenting to Mahosot Hospital, Vientiane, Laos. Methods Serum, buffy coat and urine samples were collected on admission, and follow up serum ∼10 days later. Leptospira spp. culture and microscopic agglutination tests (MAT) were performed as reference standards. Bayesian latent class modeling was performed to estimate sensitivity and specificity of each diagnostic test. Results 787 patients were included in the analysis: 4/787 (0.5%) were Leptospira culture positive, 30/787 (3.8%) MAT positive, 76/787 (9.7%) rrs qPCR positive and 20/787 (2.5%) 16SrRNA/LipL32 qPCR positive for pathogenic Leptospira spp. in ≥1 sample. Estimated sensitivity and specificity (with 95% confidence intervals [CI]) of 16SrRNA/LipL32 qPCR on serum (53.9% (33.3-81.8%); 99.6%(99.2-100%)), buffy coat (58.8% (34.4-90.9%); 99.9%(99.6-100%)) and urine samples (45.0% (27.0-66.7%); 99.6% (99.3-100%)) were comparable with those of rrs qPCR, except specificity of 16SrRNA/LipL32 qPCR on urine samples was significantly higher (99.6% (99.3-100%) vs. 92.5% (92.3-92.8%), p<0.001). Sensitivity of MAT (16% (95%CI: 6.3-29.4%)) and culture (25% (95%CI: 13.3-44.4%)) were low. Mean positive Cq values showed that buffy coat samples were more frequently inhibitory to qPCR than either serum or urine (p<0.001). Conclusions Serum and urine are better samples for qPCR than buffy coat, and 16SrRNA/LipL32 qPCR performs better than rrs qPCR on urine. qPCR on admission is a reliable rapid diagnostic tool, performing better than MAT or culture, with significant implications for clinical and epidemiological investigations of this global neglected disease.

Publisher URL: www.sciencedirect.com/science

DOI: S1198743X17305797

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