Recreating the impact of interventions in the absence of baseline data: challenges for intervention programmes
- Correspondence to Dr Jonathan M Zenilman, Johns Hopkins Bayview Medical Center, 4940 Eastern Avenue, Baltimore, MD 21224-2780, USA;
- Accepted 11 December 2009
Condom-promotion interventions have been a cornerstone of the HIV-prevention effort since the mid-1980s.1 Initial efforts were largely education-based and used simple process outcomes, such as condom-distribution statistics. Programmes rapidly became more sophisticated, and interventions based on behavioural models were rapidly implemented. One of the most challenging issues in designing and evaluating these interventions has been outcome measures. Ideally, behavioural interventions should be evaluated on disease-incident impact measures. Since HIV incidence is uncommon even in high-incident areas, intervention impact has largely used behavioural measures, such as the proportion of sexual acts in which condoms were used. These are by definition self-reported and subject to bias. In HIV/STD clinical settings, and in the context of prevention intervention studies, there is often implicit social desirability to over-report condom use. These measurement issues have a profound impact on intervention effectiveness evaluation.
Approaches to improving validity have included refining survey report methods. This has included intensive training of interviewers, and using self-administered computerised …