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