Table 1 Study quality scoring system adapted from Clark et al. [23]. Studies were assessed using specific criteria described below and scored 1 point if a criterion was fulfilled. [Adaptation by current reviewers in italic]
From: Genetic predisposition to acute kidney injury – a systematic review
Criterion | Original criteria by Clark et al. | Specific criteria |
|---|---|---|
1. Defining the Control Group | Control group described for size in relation to case group (n > case group) and ethnicity, in sufficient detail to allow replication. Cohort studies do not get a point. | Cohort studies are given a point provided that the cohort is described in sufficient detail, namely the ethnicity of a cohort is given. Prospective cohorts regarded as strong design in demonstrating causality between genetic polymorphism and the development of acute kidney injury (AKI). a Size of the control group sufficient when essentially equivalent with case group. |
2. Hardy-Weinberg Equilibrium | Case and control groups assessed for Hardy-Weinberg equilibrium (HWE). | Cohort or control group should be in HWE (p > 0.01). In case of multiple polymorphisms, the majority should be in HWE. |
3. Defining the Case Group | The disease state of interest as well as inclusion and exclusion criteria of the case group defined in sufficient detail to allow replication. | Studies that aim to investigate predisposition to AKI are given a point only if they describe the phenotype. |
4. Primer Sequence | The priming sequences used for genotyping or references to them provided. | Whenever a commercial assay was used for genotyping, a point was given as well. |
5. Describing the Methods | Genotyping method described in sufficient detail to allow replication. In addition, second validating assay performed or the accuracy of the assay validated. | Accepted quality control methods: duplicated samples or control samples included, second independent investigator analyzing the genotype calls, repeating of ambiguous results. |
6. Blinding | Genotyping performed blinded to clinical status. | |
7. Power Calculation | Prospective or retrospective power calculation performed. | No retrospective power calculations were conducted by the reviewers. |
8. Statistics | Tests of significance presented: such as p values, confidence intervals, or odds ratios. | |
9. Corrected Statistics | Corrected for the increased risk of false-positive error in the case of multiple polymorphisms studied. Should X2 or odds ratio be used, Hardy-Weinberg equilibrium is to be assessed. | Where there was only one polymorphism studied, a point was given. |
10. Replication | Study performing second, confirmatory study or confirming earlier polymorphism study. | A point was given only for studies performing exact replication of a polymorphism in association with a phenotype. |