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The challenges of accurate measurement of self‐reported sensitive behaviours in STI/HIV prevention research are highlighted by considerable epidemiological research1 and two recently completed Phase III HIV prevention trials whose null findings underscored the urgent need to improve measurement of adherence.2 Imperfect ways to assess the accuracy of self‐report exist. Current biomarkers, which validate specific behavioural assessments,3,4 are not substitutes for measuring behavioural frequencies, partnership characteristics, and co‐occurrence of behaviours (eg, microbicide use and sexual activity).
Sexual‐behaviour diaries attempt to reduce two misclassification biases: recall and social desirability.5 Few studies have assessed diary use in sub‐Saharan Africa. In this issue, Allen et al6 report on an innovative pictorial diary designed to collect sexual event‐level data. They examine diary validity through multiple reliability assessments, including a 1‐month retrospective interview completed at the end of the diary period, and compare the effects of three‐levels of interviewer support on diary reports.
Most reliability assessments posit that higher reports of sensitive behaviours (the “more is better” hypothesis) are more accurate. In the context of most HIV‐prevention trials, this interpretation is likely appropriate. Analysis of the male‐condom‐use finding in Allen et al's study—that higher reports of using condoms is more accurate—seems counterintuitive at first review. Through qualitative research, they ascertained that reports of using condoms within long‐term relationships was stigmatised and concluded that reporting no condom use was the socially desirable response. In contrast, reported condom use in prevention trials is typically much higher than that found in the general population (likely due to enhanced condom counselling and availability; trial participation; and over‐reports due to social desirability bias). A study designed for analysis by partner type (eg, regular vs exchange) would strengthen Allen et al's conclusion, as it is unlikely that reports of no condom use with exchange partners would be perceived as socially desirable as well.
The effects of interviewer support on reporting accuracy are difficult to interpret. The percentage of participants reporting any vaginal sex and sex with regular partners increased with more intensive support and was higher in the diary. What accounted for this pattern? It is unlikely that having vaginal sex with regular partners was stigmatised. Could the increased rapport with interviewers have resulted in a willingness to report sexual activity, or, rather, did participants feel obliged to report something during the twice‐weekly interviewer contact, thereby resulting in an over‐reporting of sexual activity? Also affected by intensive support were sex with irregular and casual partners, where, if “more is better”, then interviewer rapport seems to have increased honesty.
This study demonstrated high completion of a pictorial diary that could be adapted readily for use in other low‐literacy populations. I would hesitate to recommend a diary method with enhanced interviewer support, however, until further research considers the trade‐off between increased accuracy in reporting due to interviewer rapport and increased social desirability bias resulting from the loss of privacy that accompanies regular contact with an interviewer. This balance is likely to vary across cultural settings and population groups; certainly the growing literature of measurement studies conducted in sub‐Saharan Africa suggests that interview mode does influence social desirability bias.7,8,9,10,11
This paper highlights several methodological lessons: offering some level of support to participants increased diary completion, which likely reduced recall bias; understanding what behaviours are sensitive and/or stigmatised within a particular population group is critical to interpretation of behavioural self‐reports; and the role of the interviewer in influencing reporting is complex and warrants further study to guide the design of future STI/HIV prevention trials.