Improving epidemiological surveys of sexual behaviour conducted by telephone.

Background: This study assesses the impact of Telephone Audio Computer-Assisted Self-Interviewing (T-ACASI) on the reporting of sensitive (mainly heterosexual) behaviours.

Methods: A randomized experiment was embedded in a telephone survey that drew probability samples of the populations of the USA (N = 1543) and Baltimore city (N = 744). Respondents were randomly assigned to have questions asked either by a T-ACASI computer or by a human telephone interviewer.

Results: Compared with interviewer-administered telephone surveys, T-ACASI obtained more frequent reporting of a range of mainly heterosexual behaviours that were presumed to be sensitive, including recency of anal sex [adjusted odds ratio (A-OR) = 2.00, P < 0.001), sex during menstrual period (A-OR = 1.49, P < 0.001), giving oral sex (A-OR = 1.40, P = 0.001) and receiving oral sex (A-OR = 1.36, P = 0.002), and sexual difficulties for the respondent (A-OR = 1.45, P = 0.034) and their main sex partner (A-OR = 1.48, P = 0.0). T-ACASI also obtained less frequent reporting that respondent had a 'main sex partner' (A-OR = 0.56, P = 0.011) and discussed contraception prior to first sex with that sex partner (A-OR = 0.82, P = 0.094). For both males and females, T-ACASI obtained more frequent reports of first vaginal sex occurring at early ages (before ages 12 through 15). 'For males only', T-ACASI also elicited more frequent reports that first vaginal sex had 'not' occurred at later ages (i.e. by ages 20 through 24).

Conclusion: T-ACASI increases the likelihood that survey respondents will report sensitive heterosexual behaviours.