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

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.

Intra-cluster correlation estimates for HIV-related outcomes from care and treatment clinics in Dar es Salaam, Tanzania

“…This cohort allowed for the calculation of ICCs for many novel outcomes. Furthermore, while previous papers reporting ICCs for HIV-related outcomes relied exclusively on data available at baseline [18] , [19] , [20] , this paper estimated ICCs using both cross-sectional and longitudinal data. Because most cRCTs focus on longitudinal outcomes, these ICCs may better reflect future researchers' chosen study designs than ICCs calculated from baseline data alone.…”

“…Of these studies, two focused on sexual attitudes and behaviors among adolescents and young adults in the United States [18] , [19] . One study calculated ICCs for outcomes among people living with HIV, but included only a limited number of clinical outcomes and calculated ICCs using baseline data alone, which is applicable to future cross-sectional studies but not necessarily prospective studies [20] . This paper aims to provide estimates of the ICC for HIV-related clinical outcomes calculated both cross-sectionally and longitudinally among clinics supporting patients enrolled in a large urban HIV care and treatment program in Dar es Salaam, Tanzania.…”

Positive deviance for dual-method promotion among women in Uganda: study protocol for a cluster randomized controlled trial

“…The less conservative effect size of 2.43 was used because this trial will include only women who have already used HECs, unlike the prior research which recruited adolescent girls regardless of their contraceptive use [32]. Then, an intraclass correlation coefficient (ICC) of 0.006 was considered [33,34]. The ICC was adapted from a clinic-based condom use intervention in SSA [33].…”

“…Then, an intraclass correlation coefficient (ICC) of 0.006 was considered [33,34]. The ICC was adapted from a clinic-based condom use intervention in SSA [33]. The required minimum sample size was 760 after considering the ICC.…”

Positive deviance for dual-method promotion among women in Uganda: Study protocol for a cluster randomized controlled trial

“…The effect size of 2.43 was used, considering the contents of the planned intervention. Then, an intraclass correlation coefficient (ICC) of 0.006 was considered [33,34]. The ICC was adapted from a clinic-based condom use intervention in SSA [33].…”