Predictors and impact of losses to follow-up in an HIV-1 perinatal transmission cohort in Malawi

John P.A. Ioannidis, Taha E. Taha, Newton Kumwenda, Robin Broadhead, Laban Mtimavalye, Paolo Miotti, Frances Yellin, Despina G. Contopoulos-Ioannidis, Robert J. Biggar

Research output: Contribution to journalArticlepeer-review

39 Scopus citations


Background. Large simple trials which aim to study therapeutic interventions and epidemiological associations of human immunodeficiency virus (HIV) infection, including perinatal transmission, in Africa may have substantial rates of loss to follow-up. A better understanding of the characteristics and the impact of women and children lost to follow-up is needed. Methods. We studied predictors and the impact of losses to follow-up of infants born in a large cohort of delivering women in urban Malawi. The cohort was established as part of a trial of vaginal cleansing with chlorhexidine during delivery to prevent mother-to-infant transmission of HIV. Results. The HIV infection status could not be determined for 797 (36.9%) of 2156 infants born to HIV-infected mothers; 144 (6.7%) with missing status because of various sample problems and 653 (30.3%) because they never returned to the clinic. Notably, the observed rates of perinatal transmission were significantly lower in infants who returned later for determination of their infection status (odds ratio = 0.94 per month, P = 0.03), even though these infants must have had an additional risk of infection from breastfeeding. In multivariate models, infants of lower birthweight (P = 0.003) and, marginally, singletons (P = 0.09) were less likely to return for follow-up. The parents of infants lost to follow-up tended to be less educated (P < 0.001) and more likely to be in farming occupations, although one educated group, teachers and students, were also significantly less likely to rerum. Of these variables, infant birthweight, twins versus singletons, and maternal education were also associated with significant variation in the observed risk of perinatal transmission among infants of known HIV status. Conclusions. Several predictors of loss to follow-up were identified in this large HIV perinatal cohort. Losses to follow-up can impact the observed transmission rate and the risk associations in different studies.

Original languageEnglish (US)
Pages (from-to)769-775
Number of pages7
JournalInternational journal of epidemiology
Issue number4
StatePublished - 1999


  • Africa
  • HIV-1
  • Missing data
  • Perinatal transmission
  • Simple trials
  • Vaginal cleansing

ASJC Scopus subject areas

  • Epidemiology


Dive into the research topics of 'Predictors and impact of losses to follow-up in an HIV-1 perinatal transmission cohort in Malawi'. Together they form a unique fingerprint.

Cite this