Table 1.
Quality assessment of studies (SIGN 50 Methodology Checklist 3)
| Author (year) | 1.1 | 1.2 | 1.3 | 1.4 | 1.5 | 1.6 | 1.7 | 1.8 | 1.10 | 1.11 | 1.12 | 1.13 | 1.14 | 2.1 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Firns (2015) [46] | Yes | Can’t say | Can’t say | Can’t say | Can’t say | Can’t say | Yes | Yes | Yes | Yes | Can’t say | Yes | No | Cannot determine |
| Gaskins (2019) [48] | Yes | Can’t say | Yes | Does not apply | Noneb | No | Yes | Yes | Yes | Yes | No | Yes | Yes | Acceptable |
| Karayiannis (2018) [49] | Yes | Can’t say | No | No | None | No | Yes | Yes | Yes | Yes | No | Yes | Yes | Acceptable |
| Ricci (2019) [50] | Yes | Can’t say | No | No | None | No | No | Yes | Yes | Yes | No | Yes | Yes | Acceptable |
| Sugawa (2018) [51] | Yes | Can’t say | Yes | No | None | No | Yes | Yes | Yes | Yes | No | Yes | Yes | Acceptable |
| Sun (2019) [52] | Yes | Can’t say | No | No | Can’t say | No | No | Yes | No | Yes | No | Yes | Yesa | Acceptable* |
| Twigt (2012) [53] | Yes | Can’t say | No | No | None | No | Yes | Yes | No | Yes | No | Yes | Yes | Acceptable |
| Vujkovic (2010) [54] | Yes | Can’t say | No | Does not apply | None | No | Yes | Yes | Yes | Yes | No | Yes | Yes | Acceptable |
| Jahangirifar (2019) [47] | Not fully assessed c |
*Rated as acceptable for the primary outcome of embryo yield, low quality for biochemical and clinical pregnancy
a p-value
b All ‘in study cycles’ included, all participants had at least one ART ‘cycle’, number of women who dropped out not stated
c study contained a measure of association for clinical pregnancy that fell outside the confidence interval (OR 0.14, 95% CI: 0.3–0.7)
1.1 Study addresses an appropriate and clearly focused question
1.2 Groups being studied are selected from source populations comparable in all respects other than the factor under investigation
1.3 Study indicates the number of people asked to take part who did so
1.4 Likelihood that some eligible subjects might have outcome at enrolment is assessed and considered in the analysis
1.5 Study states the percentage of individuals recruited into each arm of the study who dropped out before the study was completed
1.6 Comparison is made between full participants and those lost to follow up, by exposure status
1.7 Outcomes are clearly defined
1.8 Assessment of the outcome is made blind to exposure status
1.9 Where blinding was not possible there is recognition that knowledge of exposure status could have influenced assessment of outcome (not applicable in any study)
1.10 Method of exposure assessment is reliable
1.11 Evidence from other sources is used to demonstrate that the method of outcome assessment is valid and reliable
1.12 Exposure level or prognostic factor is assessed more than once
1.13 Main potential confounders are identified and considered in the design and analysis
1.14 Confidence intervals are provided
2. 1 Overall quality based on how well the study has done to minimise the risk of bias or confounding (high, acceptable, low)