Estimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerland

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dc.contributor.authorSchöni-Affolter, Franziskaen_ZA
dc.contributor.authorKeiser, Oliviaen_ZA
dc.contributor.authorMwango, Alberten_ZA
dc.contributor.authorStringer, Jeffreyen_ZA
dc.contributor.authorLedergerber, Brunoen_ZA
dc.contributor.authorMulenga, Lloyden_ZA
dc.contributor.authorBucher, Heiner Cen_ZA
dc.contributor.authorWestfall, Andrew Oen_ZA
dc.contributor.authorCalmy, Alexandraen_ZA
dc.contributor.authorBoulle, Andrewen_ZA
dc.contributor.authorChintu, Namwingaen_ZA
dc.contributor.authorEgger, Matthiasen_ZA
dc.contributor.authorChi, Benjamin Hen_ZA
dc.date.accessioned2016-01-11T06:57:29Z
dc.date.available2016-01-11T06:57:29Z
dc.date.issued2011en_ZA
dc.description.abstractBACKGROUND: Loss to follow-up (LTFU) is common in antiretroviral therapy (ART) programmes. Mortality is a competing risk (CR) for LTFU; however, it is often overlooked in cohort analyses. We examined how the CR of death affected LTFU estimates in Zambia and Switzerland. Methods and FINDINGS: HIV-infected patients aged ≥18 years who started ART 2004-2008 in observational cohorts in Zambia and Switzerland were included. We compared standard Kaplan-Meier curves with CR cumulative incidence. We calculated hazard ratios for LTFU across CD4 cell count strata using cause-specific Cox models, or Fine and Gray subdistribution models, adjusting for age, gender, body mass index and clinical stage. 89,339 patients from Zambia and 1,860 patients from Switzerland were included. 12,237 patients (13.7%) in Zambia and 129 patients (6.9%) in Switzerland were LTFU and 8,498 (9.5%) and 29 patients (1.6%), respectively, died. In Zambia, the probability of LTFU was overestimated in Kaplan-Meier curves: estimates at 3.5 years were 29.3% for patients starting ART with CD4 cells <100 cells/µl and 15.4% among patients starting with ≥350 cells/µL. The estimates from CR cumulative incidence were 22.9% and 13.6%, respectively. Little difference was found between naïve and CR analyses in Switzerland since only few patients died. The results from Cox and Fine and Gray models were similar: in Zambia the risk of loss to follow-up and death increased with decreasing CD4 counts at the start of ART, whereas in Switzerland there was a trend in the opposite direction, with patients with higher CD4 cell counts more likely to be lost to follow-up. CONCLUSIONS: In ART programmes in low-income settings the competing risk of death can substantially bias standard analyses of LTFU. The CD4 cell count and other prognostic factors may be differentially associated with LTFU in low-income and high-income settings.en_ZA
dc.identifier.apacitationSchöni-Affolter, F., Keiser, O., Mwango, A., Stringer, J., Ledergerber, B., Mulenga, L., ... Chi, B. H. (2011). Estimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerland. <i>PLoS One</i>, http://hdl.handle.net/11427/16319en_ZA
dc.identifier.chicagocitationSchöni-Affolter, Franziska, Olivia Keiser, Albert Mwango, Jeffrey Stringer, Bruno Ledergerber, Lloyd Mulenga, Heiner C Bucher, et al "Estimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerland." <i>PLoS One</i> (2011) http://hdl.handle.net/11427/16319en_ZA
dc.identifier.citationSchöni-Affolter, F., Keiser, O., Mwango, A., Stringer, J., Ledergerber, B., Mulenga, L., ... & Chintu, N. (2011). Estimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerland. PLoS One, 6(12), e27919. doi:10.1371/journal.pone.0027919en_ZA
dc.identifier.ris TY - Journal Article AU - Schöni-Affolter, Franziska AU - Keiser, Olivia AU - Mwango, Albert AU - Stringer, Jeffrey AU - Ledergerber, Bruno AU - Mulenga, Lloyd AU - Bucher, Heiner C AU - Westfall, Andrew O AU - Calmy, Alexandra AU - Boulle, Andrew AU - Chintu, Namwinga AU - Egger, Matthias AU - Chi, Benjamin H AB - BACKGROUND: Loss to follow-up (LTFU) is common in antiretroviral therapy (ART) programmes. Mortality is a competing risk (CR) for LTFU; however, it is often overlooked in cohort analyses. We examined how the CR of death affected LTFU estimates in Zambia and Switzerland. Methods and FINDINGS: HIV-infected patients aged ≥18 years who started ART 2004-2008 in observational cohorts in Zambia and Switzerland were included. We compared standard Kaplan-Meier curves with CR cumulative incidence. We calculated hazard ratios for LTFU across CD4 cell count strata using cause-specific Cox models, or Fine and Gray subdistribution models, adjusting for age, gender, body mass index and clinical stage. 89,339 patients from Zambia and 1,860 patients from Switzerland were included. 12,237 patients (13.7%) in Zambia and 129 patients (6.9%) in Switzerland were LTFU and 8,498 (9.5%) and 29 patients (1.6%), respectively, died. In Zambia, the probability of LTFU was overestimated in Kaplan-Meier curves: estimates at 3.5 years were 29.3% for patients starting ART with CD4 cells <100 cells/µl and 15.4% among patients starting with ≥350 cells/µL. The estimates from CR cumulative incidence were 22.9% and 13.6%, respectively. Little difference was found between naïve and CR analyses in Switzerland since only few patients died. The results from Cox and Fine and Gray models were similar: in Zambia the risk of loss to follow-up and death increased with decreasing CD4 counts at the start of ART, whereas in Switzerland there was a trend in the opposite direction, with patients with higher CD4 cell counts more likely to be lost to follow-up. CONCLUSIONS: In ART programmes in low-income settings the competing risk of death can substantially bias standard analyses of LTFU. The CD4 cell count and other prognostic factors may be differentially associated with LTFU in low-income and high-income settings. DA - 2011 DB - OpenUCT DO - 10.1371/journal.pone.0027919 DP - University of Cape Town J1 - PLoS One LK - https://open.uct.ac.za PB - University of Cape Town PY - 2011 T1 - Estimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerland TI - Estimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerland UR - http://hdl.handle.net/11427/16319 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/16319
dc.identifier.urihttp://dx.doi.org/10.1371/journal.pone.0027919
dc.identifier.vancouvercitationSchöni-Affolter F, Keiser O, Mwango A, Stringer J, Ledergerber B, Mulenga L, et al. Estimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerland. PLoS One. 2011; http://hdl.handle.net/11427/16319.en_ZA
dc.language.isoengen_ZA
dc.publisherPublic Library of Scienceen_ZA
dc.publisher.departmentDepartment of Public Health and Family Medicineen_ZA
dc.publisher.facultyFaculty of Health Sciencesen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.rightsThis is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.en_ZA
dc.rights.holder© 2011 Schöni-Affolter et alen_ZA
dc.rights.urihttp://creativecommons.org/licenses/by/4.0en_ZA
dc.sourcePLoS Oneen_ZA
dc.source.urihttp://journals.plos.org/plosoneen_ZA
dc.subject.otherAntiretroviral therapyen_ZA
dc.subject.otherZambiaen_ZA
dc.subject.otherHIVen_ZA
dc.subject.otherCohort studiesen_ZA
dc.subject.otherSwitzerlanden_ZA
dc.subject.otherBody mass indexen_ZA
dc.subject.otherDeath ratesen_ZA
dc.subject.otherAntiretroviralsen_ZA
dc.titleEstimating loss to follow-up in HIV-infected patients on antiretroviral therapy: the effect of the competing risk of death in Zambia and Switzerlanden_ZA
dc.typeJournal Articleen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceArticleen_ZA
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