Table 2.

Quality Assessment According to Fowkes and Fulton^9,a

Guideline	Checklist		Cobb et al.13	Amditis and Smith10	Vu et al.12	Detterline et al.11
	Objective	Common Design
Study design appropriate to objective?	Prevalence	Cross-sectional	NA	NA	NA	NA
	Prognosis	Cohort	NA	0	0	0
	Treatment	Controlled trial	0	NA	NA	NA
	Cause	Cohort, case-control, cross-sectional	NA	NA	NA	NA
Study sample representative?	Source of sample		0	+	+	+
	Sampling method		0	+	+	+
	Sample size		0	+	++	++
	Entry criteria/exclusions		0	0	0	0
	Nonrespondents		0	0	0	0
Control group acceptable?	Definition of controls		0	0	0	0
	Source of controls		0	0	0	0
	Matching/randomization		0	+	+	+
	Comparable characteristics		0	0	0	0
Quality of measurements and outcomes?	Validity		0	0	0	0
	Reproducibility		+	+	+	+
	Blindness		NA	NA	NA	NA
	Quality control		0	0	0	0
Completeness?	Compliance		0	0	0	0
	Dropouts		0	0	0	0
	Deaths		NA	NA	NA	NA
	Missing data		+	+	+	+
Distorting influences?	Extraneous treatments		+	0	+	0
	Contamination		NA	NA	NA	NA
	Changes over time		0	0	0	0
	Confounding factors		+	0	+	+
	Distortion reduced by analysis		0	0	+	0
Summary questions	Bias: Are the results erroneously biased in a certain direction?		No	No	Yes	Yes
	Confounding: Are there any serious confounding or other distorting influences?		Yes	Yes	Yes	Yes
	Chance: Is it likely that the results occurred by chance?		No	Yes	No	No

^a++: major problem; +: minor problem; 0: no problem; NA: not applicable.