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Table 5 Risk of bias assessment tool: Adapted from the Risk of Bias Tool for Prevalence Studies developed by [33] Name of the author and year of publication

From: Prevalence and determinants of gestational diabetes mellitus in Africa based on the updated international diagnostic criteria: a systematic review and meta-analysis

Risk of Bias Item Answer:
Yes (Low Risk) or
No (High risk)
External Validity  
1. Was the study target population a close representation of the national pregnant population in relation to relevant variables?  
2. Was the sampling frame a true or close representation of the target population? (risk factors used appropriate?)  
3. Was some form of random selection used to select the sample, OR, was a census undertaken?  
4. Was the likelihood of non-participation bias minimal? (i.e. ≥75% response rate)?  
Internal Validity  
5. Were data collected directly from the subjects? (as opposed to medical records)  
6. Were acceptable diagnostic criteria for GDM used?  
7. Was a reliable and accepted method of testing for blood glucose utilised?  
8. Was the same mode of data collection used for all subjects?  
9. Was GDM tested for within the advised gestational period of 24–28 weeks?  
10. Were the numerator(s) and denominator(s) for the calculation of the prevalence of GDM appropriate?  
Summary item on the overall risk of study bias  
A. LOW RISK OF BIAS: 8 or more ‘yes’ answers. Further research is very unlikely to change our confidence in the estimate.
B. MODERATE RISK OF BIAS: 6 to 7 ‘yes’ answers. Further research is likely to have an important impact on our confidence in the estimate and may change the estimate.
C. HIGH RISK OF BIAS: 5 or fewer ‘yes’ answers. Further research is very likely to have an important impact on our confidence in the estimate and is likely to change the estimate.