Study designs of evaluations included in the review
Diagnostic cohort/cross-sectional and case-control studies were eligible for inclusion.
Specific interventions included in the review
Studies that assessed both CysC and SCr were eligible for inclusion. Studies that used the MDRD equation (which uses SCr) or a CysC-based equation were also eligible for inclusion. Assays eligible for inclusion for CysC were particle-enhanced immunoturbidimetry and particle-enhanced immunonephelometry. Assays eligible for inclusion for SCr were the standard and modified Jaffe assay and the enzymatic assay. Thresholds to define an abnormal test result ranged from 0.82 to 1.64 mg/L for CysC, and from 70.7 to 130.74 micromol/L for SCr.
Reference standard test against which the new test was compared
Studies that used the following acceptable reference standards to measure glomerular filtration rate as an indication of renal function were eligible for inclusion: exogenous inulin, Cr-EDTA, Tc-DTPA, iohexo or I-Iothalamate. Studies had to define abnormal renal function between 60 and 90 mL/minute to be included. The median threshold to define abnormal renal function was 80 mL/minute per 1.73 m2 (range: 60 to 90).
Participants included in the review
Studies of patients of all ages and in all settings were eligible for inclusion. The ages of included patients ranged from 0.2 to 93 years. The participants in the included studies were patients with various renal conditions (mixed age and paediatric), miscellaneous disorders (paediatric), diabetes, liver cirrhosis, mild impairment renal function, post renal transplant, liver diseases; non-cirrhotic patients; intensive care unit patients; geriatric (hospitalised) patients; people without diabetes; and healthy controls.
Outcomes assessed in the review
Studies that reported sufficient data to construct a 2x2 table were eligible for inclusion. The primary outcome measures were sensitivity and specificity. Likelihood ratios (LRs) and diagnostic odds ratios were also reported.
How were decisions on the relevance of primary studies made?
Two reviewers independently screened studies for inclusion and any disagreements were resolved through consensus. Authors were contacted for missing information.