Table 2.

ROB assessment (adapted from QUIPS²²and Pengel et al²³)

Study	Study participation22 Representative sample23 Data related to outcome may be different for participants and eligible non-participants/participants selected by random selection or as consecutive cases	Defined sample23 Description of source of participants and evaluation of inclusion and exclusion criteria	Study attrition/complete follow-up22 Data related to outcome may be different for completing and non-completing participants	Outcome measurement22 Measurement of the outcome may be different related to the baseline level	Study confounding22 Outcome may be distorted by another factor related to outcome	Statistical analysis and reporting22 Reported results may be spurious or biased related to analysis or reporting	Provision of data23 Studies must provide raw data, percentages, or continuous outcomes	Blinded outcome23 Assessor blinded and unaware of other measures at time of outcome was measured	Overall statement of risk of bias Number of low, moderate and high ratings
Example study	Moderate ROB Some eligibility criteria, for example, prolapse <6 mm may contribute to potential participants being excluded Suggests consecutive patients were considered	Moderate ROB Clear eligibility criteria based on detailed physical examination and radiology findings	Moderate ROB No losses to follow-up at 6 months 8 (16%) patients lost to follow-up at 12 months	Low ROB VAS 0–10 in cm Established measurement properties Measure standardised by independent assessor	Moderate ROB Possible interventions not reported	Low ROB Sufficient presentation of data No selective reporting of results	Low ROB Raw data, mean and SD reported	Low ROB Independent assessor collected data	Low 4 Moderate 4 High 0

Note: prognostic factor section of QUIPS not relevant.

QUIPS, QUality In Prognostic Studies; ROB, risk of bias; VAS, visual analogue scale.