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Table 2 Risk of bias assessment tool

From: The prevalence of insufficient iodine intake in pregnancy in Africa: protocol for a systematic review and meta-analysis

  Risk of bias item Yes = 1
No = 0
External validity
 1 Was the study target population a close representation of the national population in relation to relevant variables?  
 2 Was the sampling frame a true or close representation of the target population?  
 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?  
Internal validity
 5 Were data collected directly from the participants (as opposed to medical records)?  
 6 Were acceptable case definitions of iodine deficiency in pregnancy used?  
 7 Were reliable and accepted diagnostic methods for iodine intake utilised?  
 8 Was the same mode of data collection used for all participants?  
 9 Were the numerator(s) and denominator(s) for the calculation of the iodine intake appropriate?  
Summary of the overall risk of bias Low risk 0–3
Intermediate risk 4–6
High risk 7–9