AIDS and Behavior

, Volume 18, Issue 12, pp 2359–2365

Parameters for Sample Size Estimation from a Group-Randomized HIV Prevention Trial in HIV Clinics in Sub-Saharan Africa

  • Jun Zhang
  • Sherri L. Pals
  • Amy Medley
  • Catherine Nichols
  • Pam Bachanas
  • Deon van Zyl
  • Frieda Katuta
  • James Juma
Original Paper

DOI: 10.1007/s10461-013-0631-9

Cite this article as:
Zhang, J., Pals, S.L., Medley, A. et al. AIDS Behav (2014) 18: 2359. doi:10.1007/s10461-013-0631-9

Abstract

Sample size calculations for a group-randomized trial (GRT) require an estimate of the expected intraclass correlation coefficient (ICC). However, few ICC estimates from GRTs in HIV/AIDS research have been published, leaving investigators with little data on which to base expectations. We used data from a multi-country study to estimate ICCs for variables related to physical and mental health and HIV risk behaviors. ICCs for perceptions of physical and mental health tended to be higher than those for HIV risk behavior variables, which were higher than ICCs for CD4 count. Covariate adjustment for country and socio-demographic variables reduced most ICC estimates. For risk behavior variables, adjustment for country and socio-demographic variables reduced ICC estimates by as much as 84 %. Variability in ICC estimates has important implications for study design, as a larger ICC reduces power. ICC estimates presented in this analysis will allow more precise sample size estimates for future GRTs.

Keywords

Intraclass correlation coefficientGroup-randomized trialsSample sizeHIV/AIDS

Copyright information

© Springer Science+Business Media New York (outside the USA) 2013

Authors and Affiliations

  • Jun Zhang
    • 1
    • 2
  • Sherri L. Pals
    • 1
  • Amy Medley
    • 1
  • Catherine Nichols
    • 1
  • Pam Bachanas
    • 1
  • Deon van Zyl
    • 3
  • Frieda Katuta
    • 4
  • James Juma
    • 5
  1. 1.Division of Global HIV/AIDSCenter for Global Health, Centers for Disease Control and Prevention (CDC)AtlantaUSA
  2. 2.ICF MACROAtlantaUSA
  3. 3.Namibia CDC OfficeWindhoekNamibia
  4. 4.Namibia Ministry of Health and Social ServicesWindhoekNamibia
  5. 5.Tanzania Ministry of Health and Social WelfareDar es SalaamTanzania