Detection of asymptomatic Leishmania infection in Bangladesh by antibody and antigen diagnostic tools shows an association with post–kala-azar dermal leishmaniasis (PKDL) patients

  1. Sophie I. Owen
  2. Faria Hossain
  3. Prakash Ghosh
  4. Rajashree Chowdhury
  5. Md. Sakhawat Hossain
  6. Chris Jewell
  7. Isra Cruz
  8. Albert Picado
  9. Dinesh Mondal
  10. Emily R. Adams

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Abstract

Background

Asymptomatic Leishmania infections outnumber clinical infections on the Indian subcontinent (ISC), where disease reservoirs are anthroponotic. Diagnostics which detect active asymptomatic infection, which are suitable for monitoring and surveillance, may be of benefit to the visceral leishmaniasis (VL) elimination campaign on the ISC.

Methods

Quantitative polymerase chain reaction (qPCR), loop-mediated isothermal amplification (LAMP), and the direct agglutination test (DAT) were carried out on blood samples, and the Leishmania antigen ELISA was carried out on urine samples collected from 720 household and neighbouring contacts of 276 VL and post–kala-azar dermal leishmaniasis (PKDL) index cases, with no symptoms or history of VL or PKDL, in endemic regions of Bangladesh between September 2016 and March 2018.

Results

Of the 720 contacts of index cases, asymptomatic infection was detected in 69 (9.6%) participants by a combination of qPCR (1.0%), LAMP (2.1%), DAT (3.9%), and Leishmania antigen ELISA (3.3%). Only one (0.1%) participant was detected positive by all four diagnostic tests. Poor agreement between tests was calculated using Cohen’s kappa ( κ ) statistics; however, the Leishmania antigen ELISA and DAT in combination captured all participants as positive by more than one test. We find evidence for a moderately strong association between the index case being a PKDL case (OR 1.94, p  = 0.009), specifically macular PKDL (OR 2.12, p  = 0.004), and being positive for at least one of the four tests.

Conclusions

Leishmania antigen ELISA on urine detects active asymptomatic infection, requires a non-invasive sample, and therefore may be of benefit for monitoring transmission and surveillance in an elimination setting in combination with serology. Development of an antigen detection test in a rapid diagnostic test (RDT) format would be of benefit to the elimination campaign.

Graphical Abstract

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  1. Version published to 10.1186/s13071-021-04622-8
  2. ScreenIT

    SciScore for 10.1101/2020.05.26.20113431: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    Institutional Review Board StatementIACUC: Study ethics: This study was approved by the Ethical Review Committee (ERC) of the ICDDR,B (PR-14093).
    Consent: Adult participants provided written informed consent, and in the case of any participants under 18 years of age, a parent or guardian provided informed consent.
    Randomizationnot detected.
    BlindingResults were read by two technicians blinded to each other.
    Power Analysisnot detected.
    Sex as a biological variablenot detected.

    Table 2: Resources

    Software and Algorithms
    SentencesResources
    Samples were transported to Dhaka using a cold chain for processing and laboratory analysis using DAT and LAMP.
    LAMP
    suggested: (LAMP, RRID:SCR_001740)
    IBM SPSS Statistics 24 was used to generate receiver- operating characteristic (ROC) curves using 720 asymptomatic cases and 80 VL cases to determine the threshold in UAU/ml that gave a sensitivity of 98.8% and a specificity of 96.7%.
    SPSS
    suggested: (SPSS, RRID:SCR_002865)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).

    Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:
    A limitation of the study includes the lack of follow-up data, therefore the accuracy of the tests as predictors of progression to clinical disease is unknown. Both the DAT and Leishmania antigen ELISA capture all samples which are positive by more than one test and both utilise sample types that have a relatively non-invasive sample collection, which can be transported back to a central laboratory for testing. The specificity of all diagnostics falls below 100% for identification of L. donovani asymptomatic infection, therefore we expect some false positives on a cohort of this size; therefore, we have looked for overlap in tests which were positive. The DAT detected the highest proportion of positive individuals. The DAT detects anti-Leishmania antibodies that could be circulating from a previously cleared asymptomatic infection. However, a recent study found that DAT titers could be a useful tool to monitor transmission in an elimination setting during repeat surveys [14]. Where qPCR requires more laboratory infrastructure, the Leishmania antigen ELISA and LAMP are relatively simple techniques suitable for use in resource poor settings. Furthermore, Leishmania antigen ELISA requires a non-invasive urine sample which may aid in screening of high numbers of asymptomatic contacts. Since living with or close to a macular PKDL patient is a risk-factor for asymptomatic infection, we propose the follow-up of contacts with PKDL patients as an operational priority. Development of a...

    Results from TrialIdentifier: No clinical trial numbers were referenced.

    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.

    Results from JetFighter: We did not find any issues relating to colormaps.

    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    About SciScore

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  3. Version published to 10.1101/2020.05.26.20113431 on medRxiv