Table 2

Cochrane risk of bias tool for randomised controlled trials

EntryJudgementSupport for judgement
Beasley et al11Random sequence generation (selection bias)Low risk’We stratified participants based on never, current, or past use of DMPA and randomized them to self or clinic administration. The sequence for the 2:1 (self vs clinic administration) treatment allocation was determined using a computerized random-number generator in blocks of six. An investigator not involved with participant contact generated the allocation schedule, which was concealed until after informed consent’.
Allocation concealment (selection bias)Low risk’Group assignments for each stratum were placed in sequentially numbered opaque envelopes. After informed consent and screening were completed, the next envelope in the sequence was opened, and participants were enrolled by the study coordinator’.
Blinding of participants and personnel (performance bias)High riskBlinding not possible given the nature of the intervention (for both participants and personnel) and may have affected outcomes of continuation.
Blinding of outcome assessment (detection bias)Low riskNo blinding of outcome assessment, but the outcome measurement is not likely to be influenced by lack of blinding (particularly with Medroxyprogesterone (MPA) levels).
Incomplete outcome data addressed (attrition bias)Low riskMissing outcome data relatively balanced in numbers across intervention groups (10 of 86 in self-administration arm and 7 of 46 in clinic administration arm). While reasons for missing outcome data may be different across groups, the assumption that missing data indicated lack of continuation for both groups is strong.
Selective reporting (reporting bias)Uncertain riskNo protocol available (not described in paper or found on ClinicalTrials.gov). Insufficient information to permit judgement of ‘Low risk’ or ‘High risk’.
Other biasLow riskThe study appears to be free of other sources of bias.
Burke et al12Random sequence generation (selection bias)Low risk’Participants were randomly assigned (1:1) to receive DMPA-SC administered by a family planning provider or to be trained to self-inject DMPA-SC in accordance with a computer-generated block randomisation schedule with block sizes of four, six, and eight and stratification by study site’.
Allocation concealment (selection bias)Low risk’Allocation concealment was achieved with sequentially numbered opaque envelopes’.
Blinding of participants and personnel (performance bias)High riskBlinding not possible given the nature of the intervention (for both participants and personnel) and may have affected outcomes of continuation.
Blinding of outcome assessment (detection bias)High riskNo blinding of outcome assessment, and outcomes of continuation and adverse events/side effects may have been affected by lack of blinding. However, the statistical team remained masked until key decisions for the primary analysis were made.
Incomplete outcome data addressed (attrition bias)Low riskNo missing outcome data.
Selective reporting (reporting bias)Low riskThe study protocol is available, and all of the study’s prespecified (primary and secondary) outcomes that are of interest in the review have been reported in the prespecified way.
Other biasLow riskThe study appears to be free of other sources of bias.
Kohn et al5Random sequence generation (selection bias)Low risk’The sequence for the 1:1 (self vs clinic) treatment allocation was determined using a random number generator in blocks of six’.
Allocation concealment (selection bias)Low risk’individual assignments were placed in sequentially numbered opaque envelopes. Following screening and informed consent, study staff enrolled each willing participant and opened the next envelope in the sequence’.
Blinding of participants and personnel (performance bias)High riskBlinding not possible given the nature of the intervention (for both participants and personnel) and may have affected outcomes of continuation.
Blinding of outcome assessment (detection bias)High riskNo blinding of outcome assessment, and outcomes of continuation may have been affected by lack of blinding.
Incomplete outcome data addressed (attrition bias)Low riskNo missing outcome data.
Selective reporting (reporting bias)Low riskThe study protocol is available, and all of the study’s prespecified (primary and secondary) outcomes that are of interest in the review have been reported in the prespecified way.
Other biasLow riskThe study appears to be free of other sources of bias.
  • DMPA, depot medroxyprogesterone acetate; DMPA-SC, DMPA subcutaneous product; MPA, Medroxyprogesterone.