Table 4.

Checklist of quality assessment and risk of bias evaluation of included studies according to Fowkes and Fulton [26]

	Checklist	Akinori et al., 2000 [62]	Armah et al., 2005b [53]	Cabantous et al., 2006 [54]	Kinra and Dutta , 2013 [31]	Kwiatkowski et al., 1990 [28]	Prakash et al.,2006 [32]	Sahu et al., 2013 [33]	Thuma et al., 2011 [29]
Is the study design appropriate to objectives?	Objective common design
	Prevalence e Cross-sectional
	Prognosis Cohort
	Treatment Controlled trial
	Cohort, case-control, cross-sectional	0	0	0	0	0	0	0	0
Study sample representative?	Source of sample	0	0	0	++	0	0	0	0
	Sampling method	0	0	0	0	0	0	0	0
	Sample size	++	++	++	++	+	++	++	++
	Entry criteria/exclusion	0	0	0	+	+	+	0	0
	Non-respondents	0	0	0	0	0	0	0	0
Control group acceptable?	Definition of controls	0	0	0	0	0	0	0	0
	Source of controls	0	0	0	++	0	0	0	0
	Matching/randomization	+	++	+	+	+	+	+	+
	Comparable characteristics	0	0	0	0	0	0	0	0
Quality of measurements and outcomes?	Validity	0	++	0	0	0	0	0	0
	Reproducibility	0	0	0	0	0	0	0	0
	Blindness	++	++	++	++	++	++	++	++
	Quality control	0	0	0	0	0	0	0	0
Completeness	Compliance	0	0	0	0	0	0	0	0
	Drop outs	0	0	0	0	0	0	0	0
	Deaths	NA	NA	NA	NA	NA	NA	NA	NA
	Missing data	0	0	0	0	0	0	0	0
Distorting influences?	Extraneous treatments	0	0	0	0	0	0	0	0
	Contamination	NA	NA	NA	NA	NA	NA	NA	NA
	Changes over time	NA	NA	NA	NA	NA	NA	NA	NA
	Confounding factors	0	0	0	0	0	0	0	0
	Distortion reduced by analysis	0	0	0	0	0	0	0	0
Summary questions	Bias:
	Are the results erroneously biased in a certain direction?	NO	NO	NO	NO	NO	NO	NO	NO
	Confounding:
	Are there any serious confusing or other distorting influences?	NO	NO	NO	NO	NO	NO	NO	NO
	Chance:
	Is it likely that the results occurred by chance?	NO	NO	NO	NO	NO	NO	NO	NO

0 = No problem; + = Minor problem; ++ = Major problem; NA Not applicable