Table 2.

Scoring system for study quality used in this systematic review

Quality Criterion	Explanation	Scoring
Control Group	Was the control group equal or larger than the case group, and can it be replicated from the description given? Cohort studies were automatically given a point.	Yes = 1No = 0
Hardy-Weinberg Equilibrium	Were the case and control groups assessed for Hardy-Weinberg Equilibrium?	Yes = 1No = 0
Case Group	Can the case group be replicated from the description given, and was the disease state of interest adequately defined?	Yes = 1No = 0
Primer	Was the primer sequence used for genotyping or a reference to one provided?	Yes = 1No = 0
Reproducibility	Can the genotyping method be reproduced from the description given, and was the method validated via a second technique?	Yes = 1No = 0
Blinding	Were the researchers performing the genotyping blinded to the clinical status of the patient?	Blinded = 1Not blinded = 0
Power Calculation	Was a power calculation performed?	Yes = 1No = 0
Statistics	Were the major findings presented with well described tests of significance?	Yes = 1No = 0
Corrected Statistics	If a study examined two or more polymorphisms, were the statistics corrected for the increased risk of a false-positive finding?	Corrected = 1No correction = 0
Independent Replication	Was a second, confirmatory study performed?	Yes = 1No = 0