Interpreting sexual behaviour data: validity issues in the multicentre study on factors determining the differential spread of HIV in four African cities.

The main conclusion of the multicenter study on factors determining the differential spread of HIV in four African cities was that differences in sexual behavior could not by themselves explain the differences in HIV prevalence between the four cities. The present paper examines three potential sources of bias that could invalidate this conclusion: 1) changes in sexual behavior since the start of the HIV epidemics; 2) bias due to the low response rates of men; and 3) bias in reported sexual behavior. To assess whether there have been any changes in sexual behavior over time selected parameters of sexual behavior were compared between different age groups in the four cities. The maximum likely extent of bias due to non-participation of men in Yaounde Kisumu and Ndola was assessed with a simulation exercise in which records of non- participants were replaced with records of “low activity men” in Yaounde and “high activity men” in Kisumu and Ndola. To assess the validity of the sexual behavior data internal validity checks were carried out: comparing biological data on sexually transmitted infections (STIs) with reports; comparing reports of spouses; and comparing numbers of sex partners reported by men and women. A fourth method consisted of comparing the findings of the multicenter study with an external source Demographic and Health Surveys (DHS). There were differences in sexual behavior between the younger and the older age groups in all four cities but there was no evidence of a shift towards safer sexual behavior in the high HIV prevalence cities. After simulating results for male non-participants in Yaounde Kisumu and Ndola the median lifetime number of sex partners was similar in Yaounde Kisumu and Ndola. By testing for various STIs among men and women aged 15-24 years who reported that they had never had sexual intercourse the authors could establish that in all four cities at least 1-9% of men and 6-18% of women had misreported their sexual activity. The number of non-spousal partners in the past 12 months reported by men was two to three times higher than the number reported by women as has been found in other studies. The most consistent differences between the authors survey and the DHS were found in the numbers of non-spousal partners in the past 12 months reported by never-married men and women. In all four cities participants reported more non-spousal partners in the DHS than in the authors survey. In all four cities the authors found evidence that men as well as women misreported their sexual behavior but overall it seems that under-reporting of sexual activity was not more common or more serious in the two high HIV prevalence cities than in the two low HIV prevalence cities. The authors believe that the main conclusions of the multicenter study still hold. (authors)