Peipert 2008.

Methods	DESIGN: Two‐centre RCT LENGTH OF FOLLOW‐UP: 24 months (also 6, 12 and 18 months but data not reported). DATA ANALYSIS: Stated that all comparisons among the primary outcomes were made according to the intention to treat principle (no definition of intention to treat was provided). Different methods for analysing missing data were evaluated for applicability, but not whether any were actually used. ATTRITION RATE: Completed 24 month follow up: Group 1=166/272 (61%); Group 2=180/270 (67%). UNIT OF DATA ANALYSIS: Individuals (as randomised). SAMPLE SIZE CALCULATION: Based on 3 assumptions: that the baseline event rate for either an unintended pregnancy or an incident STI was at least 30% over 12 months in the high‐risk sample; the intervention would reduce these to 15% or less; and the attrition rate would be 25% over 2 years. Approximately 250 participants would need to be enrolled in each arm to detect a 2‐fold change in dual method use from approximately 15% to 30% (intervention RR=2.0) or a 50% difference in incidence of an STI or unintended pregnancy (intervention RR=0.5), with 90% power and type I error rate 2.5%. The authors stated that despite using an a priori sample size calculation and recruiting more than 500 participants, the statistical power to address some outcomes was limited. Approximately 28 to 31% of participants reported male condom use before intervention, which increased to more than 40% after intervention in both groups. According to the authors, this increase in condom use in Group 2 limited the power to assess differences. EQUIVALENT STUDY GROUPS AT BASELINE: Stated that, overall, randomisation achieved similar characteristics in the two study groups, but there were some slight imbalances: Participants in Group 2 were more likely to have had less than a high school education (29% versus 21%; P = 0.03), a history of STI (51% versus 43%; P = 0.07) and were more likely to have had 2 or more sexual partners in the past month (20% versus 11%; P = 0.02). PROCESS EVALUATION: Not reported.
Participants	NUMBER RANDOMISED: 542 (Asterisks indicate minor differences in reported and correct percentages; the correct percentages are reported here) AGE, n (%): <20 years: Group 1= 82 (30); Group 2 =73 (27); 20 to 24 years: Group 1 = 140 (51); Group 2 = 133 (49); ≥25 years: Group 1 = 50 (18); Group 2 = 64 (24). SOCIO‐ECONOMIC STATUS: Marital status, n (%): Single, never married: Group 1 = 240 (88*): Group 2 =n 245 (91*); Married: Group 1 = 17 (6); Group 2 = 12 (4); Separated/divorced/widowed: Group 1 = 12 (4); Group 2 = 15 (6). Education, n (%): Less than high school: Group 1 = 56 (21); Group 2 = 77 (29); High school/GED: Group 1 = 105 (39); Group 2 = 95 (35); 2 year degree or some college: Group 1 = 87 (32); Group 2 = 76 (28); 4 year degree or more: Group 1 = 24 (9); Group 2 = 21 (8). ETHINCITY/RACE, n (%): White, non‐Hispanic: Group 1 = 125 (46); Group 2 = 118 (44); Black, non‐Hispanic: Group 1 = 70 (26); Group 2 = 71 (26); Hispanic: Group 1 = 43 (16); Group 2 = 50 (19); Other: Group 1 = 34 (13); Group 2 = 31 (11). LOCATION: USA; Providence, Rhode Island (urban). PREVIOUS STI, n (%): Group 1 = 116 (43); Group 2 = 137 (51). SEXUAL RISK BEHAVIOUR: History of unplanned pregnancy, n (%): Group 1 = 127 (47); Group 2 = 136 (50*). Contraceptive use, n (%): None: Group 1 = 88 (32); Group 2 = 96 (36). Hormonal: Group 1 = 95 (35); Group 2 = 82 (30); Male condoms: Group 1 = 75 (28); Group 2 = 84 (31). Lifetime sexual partners, n (%): 1 to 2: Group 1 = 34 (13); Group 2 = 36 (13); 3 to 5: Group 1 = 99 (36); Group 2 = 90 (33); 6 to 10: Group 1 = 69 (25); Group 2 = 60 (22); ≥11: Group 1 = 70 (26); Group 2 = 83 (31). Sexual partners in past month, n (%): 0: Group 1 = 40 (15); Group 2 = 33 (12); 1: Group 1 = 203 (75); 183 (68); ≥2: Group 1 = 28 (10*); Group 2 = 53 (20). New main partner in past 6 months, n (%): Group 1 = 71 (26); Group 2 = 68 (25). Inclusion criteria stated that women were sexually active with a male partner in the past 6 months and at high risk for unintended pregnancy or STI. OTHER: All participants were negative for STIs and pregnancy at baseline (or were treated with direct observed treatment with a highly active antimicrobial). The authors reported the diagnostic criteria for PID and duration of infection with herpes simplex virus (HSV). Only participants with new‐onset HSV infection after randomisation were eligible for this STI outcome.
Interventions	GROUP 1: Individual‐tailored dual contraception interactive computer intervention (n = 272) YEAR STARTED: October 1999 to October 2003. PROVIDER(S): None reported; intervention was self‐administered using an interactive computer system. SETTING(S): Secondary care (hospital focusing on women and infants). TYPE: Information on dual contraception delivered by interactive computer system that gave on‐screen and printed dual contraception feedback; tailored to an individual's readiness to change their condom and contraceptive behaviours, according to the stages of change in the Transtheoretical Model. The intervention comprised three different sessions, at baseline, 1 month and 2 months. Participants were also given a packet of information about dual methods and a sample condom. DURATION: Stated that participants were scheduled to receive the 3 sessions over period of 80 days; however, also stated that sessions were delivered up to 2 months, which would approximate to 60 days. Duration of individual sessions not reported. THEORETICAL BASIS: Transtheoretical Model. STIs COVERED: STIs in general (HIV not mentioned). GROUP 2: Enhanced standard care computer intervention (n = 270) YEAR STARTED: As Group 1. PROVIDER(S): As Group 1. SETTING(S): As Group 1. TYPE: Standard contraceptive and STI prevention information delivered by interactive computer system that gave on‐screen and printed standard care feedback; not tailored to individual participants. Included information about dual contraception method use. Comprised one session at baseline. Participants were also given a packet of information about dual methods and a sample condom. DURATION: Not reported. THEORETICAL BASIS: Not reported. STIs COVERED: STIs in general, including HIV.
Outcomes	PRIMARY BEHAVIOURAL: Self‐reported use of dual methods of contraception (hormonal contraception plus barrier method; male condoms plus female condoms; condoms plus spermicide; or intrauterine device or sterilisation plus a barrier method). PRIMARY BIOLOGICAL: Incidence or recurrence of STI (gonorrhoea, chlamydia, Herpes simplex, trichomoniasis or acute PID) and/or unintended pregnancy. SECONDARY (PROCESS MEDIATING): Stages of change for condom and contraceptive use; pros and cons of condom and contraceptive use; self‐efficacy for condom and contraceptive use; processes of condom use; sexual assertiveness; anticipated partner reaction; victimisation history; and substance use.
Notes	COST DATA: Reported only that recruited women received $25 at the time of randomisation and $20 at each annual examination to reimburse for child care and transportation. Participants in the intervention group also received an additional $10 for returning for 30‐day and 60‐day components of the computer intervention.
Risk of bias
Bias	Authors' judgement	Support for judgement
Adequate sequence generation?	Low risk	Stated that participants were assigned by a computer‐generated random sequence into the intervention or control groups. Randomisation was stratified by study site and baseline contraceptive group.
Allocation concealment?	Low risk	Stated that random assignment was separated from the executor of assignment (phone interviewer and nurse practitioner doing examinations) and that randomisation, allocation and concealment were all done by the computer at the participant's baseline assessment ensuring that assignment was free from bias.
Blinding? All outcomes	Unclear risk	Stated that although true masking was difficult in this setting, every effort was made to mask the follow‐up evaluators to the treatment allocation (but no details were provided).
Incomplete outcome data addressed? All outcomes	Unclear risk	The sample sizes (n, N and %) given for the primary outcomes suggest that all randomised participants were analysed in the groups to which they were randomised. However, it is unclear how the missing data were handled to achieve this. The choice of imputation method used was not reported. Attrition rates were balanced between trial groups, but no reasons were given for attrition and it is therefore not clear whether reasons for attrition differed between trial groups.
Free of selective reporting?	Unclear risk	Most aspects of the outcomes described in the methods were also reported in the results section. Some specific aspects of outcomes described in the methods (e.g. the type and combination of dual use method) were subsumed within more general outcomes presented in the results (e.g. reported as any dual method use). Also, certainty of STI diagnosis (e.g. possible, probable) were not presented in the results section so it is not fully clear how the diagnosis classes relate to the results presented.
Free of other bias?	High risk	Imbalance between trial groups on three relevant variables at baseline (see 'Methods' above).