Table 2

Risk of bias assessment of individual studies (n=21)

 Article 1. Was the purpose of the study clearly defined in the abstract and introduction?* 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-response bias minimal? 5. Were data collected directly from the subjects? 6. Was an acceptable case definition used in the study? 7. Was the study instrument that measured valid and reliable? 8. Was the same mode of data collection used for all subjects? 9. Was the length of the shortest prevalence period for the parameter of interest appropriate? 10. Were the numerator(s) and denominator(s) for the parameter of interest appropriate? Pirson and Pirlot (1990)18 Yes No No Yes Partially No Partially Partially Yes Yes Linenger et al (1993)19 Partially No No No Partially Yes Partially Yes Yes Yes Shwayhat et al (1994)20 Yes Yes Partially Yes Partially Yes Partially Yes Yes Yes Kragh et al (1996)22 Yes No Partially No No Yes No No Yes Yes Miser et al (1995)21 Yes No No No Yes Partially No No Yes No Ensign et al (2000)24 Partially No No No Yes No No Yes No Yes Schumacher et al (2000)23 Yes No No No No Yes Partially Yes Yes Yes Kotwal et al (2004)25 Partially No No No Partially Yes No Partially Yes Partially Hughes and Weinrauch (2008)26 Yes No No No No No No Partially Yes Partially Lynch and Pallis (2008)37 Yes Partially No No No No Partially Yes Yes No Hollingsworth (2009)28 Yes Yes No Yes Yes Partially No Yes No No Reynolds et al (2009)27 Yes No No No Partially Yes No Yes Yes Yes Abt et al (2014)29 Yes Partially No Yes Yes Yes No Yes Yes Partially Teyhen et al (2015)30 Yes Yes Partially No Partially Yes Partially Yes Yes No Lovalekar et al (2016)31 Yes No No No No Yes No Partially Yes No Heebner et al (2017)34 Yes No No No No Yes Partially Yes Yes Partially Lovalekar et al (2017)32 Yes Yes No No Yes Yes Partially Partially No No Lovalekar et al (2017)33 Yes No No No Partially Yes Partially Partially Yes Partially Lovalekar et al (2018)35 Yes No No No No Yes No Partially Yes Partially Teyhen et al (2018)36 Yes Yes Partially No Partially Partially Partially Partially Yes Yes Dijksma et al (2020)17 Yes Partially Partially Yes Partially Yes Partially Partially Yes Partially