Interpretation of serial interferon-gamma test results to measure new tuberculosis infection among household contacts in Zambia and South Africa

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dc.contributor.authorSloot, Rosaen_ZA
dc.contributor.authorShanaube, Kwameen_ZA
dc.contributor.authorClaassens, Marelien_ZA
dc.contributor.authorTelisinghe, Lilyen_ZA
dc.contributor.authorSchaap, Aben_ZA
dc.contributor.authorGodfrey-Faussett, Peteren_ZA
dc.contributor.authorAyles, Helenen_ZA
dc.contributor.authorFloyd, Sianen_ZA
dc.date.issued2020-10-15
dc.descriptionCITATION: Sloot, R., et al. 2020. Interpretation of serial interferon-gamma test results to measure new tuberculosis infection among household contacts in Zambia and South Africa. BMC Infectious Diseases, 20:760, doi:10.1186/s12879-020-05483-9.
dc.descriptionThe original publication is available at https://bmcinfectdis.biomedcentral.com
dc.description.abstractBackground: A more stringent QuantiFERON-TB Gold In-Tube (QFT) conversion (from negative to positive) definition has been proposed to allow more definite detection of recent tuberculosis (TB) infection. We explored alternative conversion definitions to assist the interpretation of serial QFT results and estimate incidence of TB infection in a large cohort study. Methods: We used QFT serial results from TB household contacts aged ≥15 years, collected at baseline and during two follow-up visits (2006–2011) as part of a cohort study in 24 communities in Zambia and South Africa (SA). Conversion rates using the manufacturers’ definition (interferon-gamma (IFN-g) < 0.35 to ≥0.35, ‘def1’) were compared with stricter definitions (IFN-g < 0.2 to ≥0.7 IU/ml, ‘def2’; IFN-g < 0.2 to ≥1.05 IU/ml, ‘def3’; IFN-g < 0.2 to ≥1.4 IU/ml, ‘def4’). Poisson regression was used for analysis. Results: One thousand three hundred sixty-five individuals in Zambia and 822 in SA had QFT results available. Among HIV-negative individuals, the QFT conversion rate was 27.4 per 100 person-years (CI:22.9–32.6) using def1, 19.0 using def2 (CI:15.2–23.7), 14.7 using def3 (CI:11.5–18.8), and 12.0 using def4 (CI:9.2–15.7). Relative differences across def1-def4 were similar in Zambia and SA. Using def1, conversion was less likely if HIV positive not on antiretroviral treatment compared to HIV negative (aRR = 0.7, 95%CI = 0.4–0.9), in analysis including both countries. The same direction of associations were found using def 2–4. Conclusion: High conversion rates were found even with the strictest definition, indicating high incidence of TB infection among household contacts of TB patients in these communities. The trade-off between sensitivity and specificity using different thresholds of QFT conversion remains unknown due to the absence of a reference standard. However, we identified boundaries within which an appropriate definition might fall, and our strictest definition plausibly has high specificity.
dc.description.urihttps://bmcinfectdis.biomedcentral.com/articles/10.1186/s12879-020-05483-9
dc.description.versionPublisher's version
dc.format.extent19 pagesen_ZA
dc.identifier.citationSloot, R., et al. 2020. Interpretation of serial interferon-gamma test results to measure new tuberculosis infection among household contacts in Zambia and South Africa. BMC Infectious Diseases, 20:760, doi:10.1186/s12879-020-05483-9
dc.identifier.issn1471-2334 (online)
dc.identifier.otherdoi:10.1186/s12879-020-05483-9
dc.identifier.urihttp://hdl.handle.net/10019.1/110420
dc.language.isoen_ZAen_ZA
dc.publisherBioMed Centralen_ZA
dc.rights.holderAuthors retain copyrighten_ZA
dc.subjectTuberculosisen_ZA
dc.subjectTuberculosis -- Diagnosisen_ZA
dc.subjectInterferon-gamma -- Test resultsen_ZA
dc.subjectQuantiFERONen_ZA
dc.subjectTuberculosis -- Infectionsen_ZA
dc.titleInterpretation of serial interferon-gamma test results to measure new tuberculosis infection among household contacts in Zambia and South Africaen_ZA
dc.typeArticleen_ZA
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