Compared daily diaries with surprise retrospective survey 6–12 months later

Under-reported number of partners (p=0.02) on survey

Over-reported frequency of any sex, vaginal sex and oral sex on survey (all p<0.01)

Over-reported condom use for vaginal (p=0.02) and oral sex (p=0.06) on survey

Vaginal sex was reported four times more often in retrospective survey than diaries

No significant differences in recall of anal sex

Participants could not accurately predict their recall accuracy on retrospective survey

Compared twice weekly, weekly and biweekly diaries with 3 month retrospective survey

Non-significant under-reporting on retrospective survey

Most concordance correlation coefficient and κ statistics ≥80%

Compared daily diary with retrospective survey

Over-reported receptive oral and anal sex on survey (all p<0.05)

Greater frequency of giving oral sex (p<0.05), receiving oral sex (p<0.01), and higher number of sexual events (p<0.01) were associated with over-reporting on survey

Greater frequency of unprotected insertive anal sex was associated with under-reporting on survey (p<0.001)

28–85% of participants over-reported or under-reported each behaviour on the retrospective survey

Compared online, text-message and paper weekly diaries with retrospective survey

Correlation was high for proportion of partners considered ‘regular’ (0.87), frequency of sex (0.76), frequency of condom use (0.76) and STI risk (0.74)

Correlation was lower for number of partners (0.63) and proportion of partners considered ‘new’ (0.57)

Compared recall from active diary participants with controls

Controls had 0.9 more new male partners than diary subjects (p=0.05)

Controls had significantly greater increases in frequency of anal sex (p=0.01), frequency of unprotected anal sex (p<0.01) and any unprotected anal sex (p<0.01)

Controls had significantly higher STI and HIV diagnosis incidence rates (26.1%) than active diary participants (4.8%, p=0.01)

No evidence of dose-response by diary frequency

Author explanation: difference in HIV/STI incidence indicates that risky behaviour may have actually differed over time between groups; attributed to diaries because of controlled nature of study

Diary completion fell significantly over time (-0.61%/week, p<0.05)

Reports of vaginal sex decreased significantly over time (−0.61%/week, p<0.05)

Greater decrease in vaginal sex was reported in 18–20-year-olds (−0.91%/week), 27–29 year-olds (−0.83%/week), men (−0.80%/week) and patients without STI at enrolment (−0.68%/week) (all p<0.05)

Author explanation: slight differences in reported behaviour during study may be due to subtle changes in behaviour over time, not diary participation

Statistically significant decline in giving oral sex, receiving oral sex, insertive anal sex and unprotected receptive anal sex over time (all p<0.05)

Author explanation: diary completion leads to self-monitoring, which causes participants to reduce risky behaviours over time

No evidence of reactivity

No evidence of reactivity