Evaluation of the EIE-IgM-Leptospirose assay for the serodiagnosis of leptospirosis

Prospective evaluation of accuracy and clinical utility of the Dual Path Platform (DPP) assay for the point-of-care diagnosis of leptospirosis in hospitalized patients

Early detection of leptospirosis with field-ready diagnostics may improve clinical management and mitigate outbreaks. We previously validated the point-of-care Dual Path Platform (DPP) for leptospirosis with sera in the laboratory. This prospective study compares the diagnostic accuracy and clinical utility of the DPP using finger stick blood (FSB) against the serum DPP, venous whole blood (VWB) DPP, IgM-ELISA, and clinical impression. We sequentially enrolled 98 patients hospitalized for acute febrile illnesses, of which we confirmed 32 by leptospirosis reference tests. Among syndromes consistent with classic leptospirosis, the FSB DPP showed similar sensitivity and specificity (Se 93% and Sp 80%), and positive and negative predictive values (PPV 74% and NPV 95%), to VWB DPP (Se 96%, Sp 75%, PPV 68%, and NPV 97%), serum DPP (Se 85%, Sp 87%, PPV 79%, and NPV 91%) and IgM-ELISA (Se 81%, Sp 100%, PPV 100%, and NPV 90%). The FSB DPP provided a favorable likelihood ratio profile (positive LR 4.73, negative LR 0.09) in comparison to other assays and clinical impression alone. Additionally, we identified four of five leptospirosis-associated meningitis patients by whole blood DPP, none of which clinicians suspected. This demonstrates potential for the DPP in routine detection of this less common syndrome. The FSB DPP demonstrated similar discrimination for severe human leptospirosis compared with serum assays, and it is a simpler option for diagnosing leptospirosis. Its performance in other epidemiological settings and geographic regions, and for detecting atypical presentations, demands further evaluation.

The reliable, portable, point-of-care DPP assay effectively discriminates case status for patients presenting to hospital with acute febrile syndromes consistent with classic leptospirosis. Diagnostic accuracy of the finger stick DPP using the initial acute-phase specimen at the bedside is similar to serum DPP and IgM-ELISA, yet diagnosticians can perform the DDP assay in 20 minutes without laboratory equipment. The finger stick DPP expands rapid diagnostic options at the bedside for severe leptospirosis in humans.

IgM ELISA for leptospirosis diagnosis: a systematic review and meta-analysis

Abstract A systematic review with meta-analysis was performed to estimate the accuracy of IgM ELISA for Leptospirosis diagnosis. A search of Medline, Lilacs, Embase, Cochrane Central Register of Controlled Trials and Grey literature (Google Scholar and British Library) was conducted. The medical subject headings (MeSHs) and the words “leptospirosis”, “human leptospirosis” and “IgM ELISA” were used. Fifty-two studies were analyzed, which included 10,775 samples. The pooled sensitivity of all the studies was 86% (CI 95%, 85%-87%) and specificity was 90% (CI 95%, 89%-91%). In studies of the acute phase, the sensitivity and specificity were 84% (CI 95%, 82%-85%) and 91% (CI 95%, 90%-91%), respectively. In conclusion, IgM ELISA is sensitive for use as an initial screen for leptospiral infections.

Development and evaluation of an immunochromatographic assay to detect serum anti-leptospiral lipopolysaccharide IgM in acute leptospirosis

Leptospirosis is a common life-threatening disease worldwide. However, its diagnosis is frequently ineffective because the gold standard bacterial culture and microscopic agglutination test (MAT) are usually positive 1-2 weeks after the disease onset. We thus developed an immunochromatographic assay (LEPkit) to detect serum anti-leptospiral lipopolysaccharide (LPS) IgM for rapid diagnosis of acute leptospirosis. Using referenced sera of 77 leptospirosis and 91 non-leptospirosis cases, LEPkit yielded 97.4% sensitivity, 94.5% specificity, 93.8 positive predictive value (PPV), 97.7% negative predictive value (NPV), and 95.8% accuracy. The stability of this kit stored for up to 18 months and its reproducibility were confirmed. Testing in 74 new cases using samples at admission-phase and subsequent paired samples (total n = 135), overall sensitivity was 98.5%, whereas that of culture and single MAT (≥1:400) was 15.6% and 35.6%, respectively. When only the samples at admission-phase were used (n = 74), the sensitivity remained at 98.7%, whereas that of culture and single MAT (≥1:400) was 28.4% and 13.5%, respectively. In summary, our LEPkit was far more effective than any conventional methods for the diagnosis of acute leptospirosis, especially within the first few days after the disease onset. The ease of use, stability and reproducibility further enhance its feasibility for clinical use on-site.

Rapid tests for diagnosis of leptospirosis: current tools and emerging technologies

Leptospirosis is an emerging zoonosis with a worldwide distribution but is more commonly found in impoverished populations in developing countries and tropical regions with frequent flooding. The rapid detection of leptospirosis is a critical step to effectively manage the disease and to control outbreaks in both human and animal populations. Therefore, there is a need for accurate and rapid diagnostic tests and appropriate surveillance and alert systems to identify outbreaks. This review describes current in-house methods and commercialized tests for the rapid diagnosis of acute leptospirosis. It focuses on diagnostic tests that can be performed with minimal training and limited equipment in less-developed and newly industrialized countries, particularly in resource-limited settings and with results in minutes to less than 4 hours. We also describe recent technological advances in the field of diagnostic tests that could allow for the development of innovative rapid tests in the near future.

Accuracy of a dual path platform (DPP) assay for the rapid point-of-care diagnosis of human leptospirosis

BACKGROUND

Diagnosis of leptospirosis by the gold standard serologic assay, the microscopic agglutination test (MAT), requires paired sera and is not widely available. We developed a rapid assay using immunodominant Leptospira immunoglobulin-like (Lig) proteins in a Dual Path Platform (DPP). This study aimed to evaluate the assay's diagnostic performance in the setting of urban transmission.

METHODOLOGY

We determined test sensitivity using 446 acute and convalescent sera from MAT-confirmed case-patients with severe or mild leptospirosis in Brazil. We assessed test specificity using 677 sera from the following groups: healthy residents of a Brazilian slum with endemic transmission, febrile outpatients from the same slum, healthy blood donors, and patients with dengue, hepatitis A, and syphilis. Three operators independently interpreted visual results without knowing specimen status.

RESULTS

The overall sensitivity for paired sera was 100% and 73% for severe and mild disease, respectively. In the acute phase, the assay achieved a sensitivity of 85% and 64% for severe and mild leptospirosis, respectively. Within seven days of illness onset, the assay achieved a sensitivity of 77% for severe disease and 60% for mild leptospirosis. Sensitivity of the DPP assay was similar to that for IgM-ELISA and increased with both duration of symptoms (chi-square regression P = 0.002) and agglutinating titer (Spearman ρ = 0.24, P<0.001). Specificity was ≥93% for dengue, hepatitis A, syphilis, febrile outpatients, and blood donors, while it was 86% for healthy slum residents. Inter-operator agreement ranged from very good to excellent (kappa: 0.82-0.94) and test-to-test reproducibility was also high (kappa: 0.89).

CONCLUSIONS

The DPP assay performed acceptably well for diagnosis of severe acute clinical leptospirosis and can be easily implemented in hospitals and health posts where leptospirosis is a major public health problem. However, test accuracy may need improvement for mild disease and early stage leptospirosis, particularly in regions with high transmission.

Validation of a case definition for leptospirosis diagnosis in patients with acute severe febrile disease admitted in reference hospitals at the State of Pernambuco, Brazil

INTRODUCTION: Leptospirosis is often mistaken for other acute febrile illnesses because of its nonspecific presentation. Bacteriologic, serologic, and molecular methods have several limitations for early diagnosis: technical complexity, low availability, low sensitivity in early disease, or high cost. This study aimed to validate a case definition, based on simple clinical and laboratory tests, that is intended for bedside diagnosis of leptospirosis among hospitalized patients. METHODS: Adult patients, admitted to two reference hospitals in Recife, Brazil, with a febrile illness of less than 21 days and with a clinical suspicion of leptospirosis, were included to test a case definition comprising ten clinical and laboratory criteria. Leptospirosis was confirmed or excluded by a composite reference standard (microscopic agglutination test, ELISA, and blood culture). Test properties were determined for each cutoff number of the criteria from the case definition. RESULTS: Ninety seven patients were included; 75 had confirmed leptospirosis and 22 did not. Mean number of criteria from the case definition that were fulfilled was 7.8±1.2 for confirmed leptospirosis and 5.9±1.5 for non-leptospirosis patients (p<0.0001). Best sensitivity (85.3%) and specificity (68.2%) combination was found with a cutoff of 7 or more criteria, reaching positive and negative predictive values of 90.1% and 57.7%, respectively; accuracy was 81.4%. CONCLUSIONS: The case definition, for a cutoff of at least 7 criteria, reached average sensitivity and specificity, but with a high positive predictive value. Its simplicity and low cost make it useful for rapid bedside leptospirosis diagnosis in Brazilian hospitalized patients with acute severe febrile disease.

Recombinant vaccines against leptospirosis

Leptospirosis is an important neglected infectious disease that occurs in urban environments, as well as in rural regions worldwide. Rodents, the principal reservoir hosts of pathogenic Leptospira spp., and other infected animals shed the bacteria in their urine. During occupational or even recreational activities, humans that come into direct contact with infected animals or with a contaminated environment, particularly water, are at risk of infection. Prevention of urban leptospirosis is largely dependent on sanitation measures that are often difficult to implement, especially in developing countries. Vaccination with inactivated whole-cell preparations (bacterins) has limited efficacy due to the wide antigenic variation of the pathogen. Intensive efforts towards developing improved recombinant vaccines are ongoing. During the last decade, many reports on the evaluation of recombinant vaccines have been published. Partial success has been obtained with some surface-exposed protein antigens. The combination of protective antigens and new adjuvants or delivery systems may result in the much-needed effective vaccine.

Leptospirosis in a subsistence farming community in Brazil

Leptospirosis has been reported in rural areas of Brazil. However, there is limited information about the exposure risk or the risk of Leptospira infection for rural-based populations. A cross-sectional study was carried out in order to determine the prevalence and risk factors for prior Leptospira infection in a rural subsistence farming region of the state of Rio Grande do Norte, an area in which outbreaks of leptospirosis have occurred. Among 290 individuals enrolled, 44 (15.2%) had anti-Leptospira IgM antibodies as determined by IgM ELISA. Infection tended to occur with activities related to the rice fields (P=0.08). Our findings indicate that Leptospira infection occurs even in years of low rainfall, and may have an important impact among poor rural-based subsistence farmers in Brazil. Additional studies are needed to characterize the mode of transmission in this region.

Evaluation of four whole-cell Leptospira-based serological tests for diagnosis of urban leptospirosis

Four serologic assays for leptospirosis had sensitivities of 72 to 88% and specificities of 88 to 100% in the setting of highly endemic urban transmission, indicating that assays using enzyme-linked immunosorbency and rapid formats may be used as alternatives to the microscopic agglutination test for diagnosing urban leptospirosis. Testing a second sample will be required in cases with an initial negative result, since sensitivity was low (46 to 68%) during the first week of illness.