Rapid, actionable diagnosis of urban epidemic leptospirosis using a pathogenic Leptospira lipL32-based real-time PCR assay

Abstract

BackgroundWith a conservatively estimated 1 million cases of leptospirosis worldwide and a 5–10% fatality rate, the rapid diagnosis of leptospirosis leading to effective clinical and public health decision making is of high importance, and yet remains a challenge.MethodologyBased on parallel, population-based studies in two leptospirosis-endemic regions in Brazil, a real-time PCR assay which detects lipL32, a gene specifically present in pathogenic Leptospira, was assessed for the diagnostic effectiveness and accuracy. Patients identified by active hospital-based surveillance in Salvador and Curitiba during large urban leptospirosis epidemics were tested. Real-time PCR reactions were performed with DNA-extracted samples obtained from 127 confirmed and 23 unconfirmed cases suspected of leptospirosis, 122 patients with an acute febrile illness other than leptospirosis, and 60 healthy blood donors.Principal findingsThe PCR assay had a limit of detection of 280 Leptospira genomic equivalents/mL. Sensitivity for confirmed cases was 61% for whole blood and 29% for serum samples. Sensitivity was higher (86%) for samples collected within the first 6 days after onset of illness compared to those collected after 7 days (34%). The real-time PCR assay was able to detect leptospiral DNA in blood from 56% of serological non-confirmed cases. The overall specificity of the assay was 99%.ConclusionsThese findings indicate that real-time PCR may be a reliable tool for early diagnosis of leptospirosis, which is decisive for clinical management of severe and life-threatening cases and for public health decision making.

When and what to test for: A cost-effectiveness analysis of febrile illness test-and-treat strategies in the era of responsible antibiotic use

“…Increasing patients' delay in seeking care from 1 day to 10 days increased costs threefold, and DALYs sevenfold (S3 Table, S4 Table). This is consistent with recommendations for early diagnosis and treatment in order to avoid worsened health outcomes [34,35]. For patients referred to hospitals on their first or fourth day of illness, we found that PCR-led strategies were more likely to be on the effectiveness frontier compared to RDT-led strategies (Figs 1 and 2, S3 Fig, S4 Fig) since PCR tests had higher accuracy in the early stage of illness where RDTs were more accurate in the later stage (S1 Table).…”

Leptospirosis manifested with severe pulmonary haemorrhagic syndrome successfully treated with venovenous extracorporeal membrane oxygenation

“…The accuracy of this test was evident in several studies with a sensitivity of 61%–86% and a specificity of 99%–100%. Both high yield and rapidity of the test make it practical in the diagnosis of severe leptospirosis, which needs prompt treatment, and can avoid unnecessary immunosuppressive drugs during management of treatable DAHs 26–28. Moreover, we found that Leptospira IgM from blood samples was negative in day 1, but turned to positive result later in day 8 (Department of Medical Sciences, Thailand, 2018; sensitivity 92%, specificity 98.7%; compare with microscopic agglutination test).…”

Diagnostic accuracy of genetic markers and nucleic acid techniques for the detection of Leptospira in clinical samples: A meta-analysis

“…The studies included were conducted in different countries and were published from 1992 to 2018. Some of the included studies used different methods; thus, the data were reported as separate independent studies [12,[22][23][24][25][26][27][28][29][30][31][32].…”