Serum cystatin C as a marker to identify patients with moderately impaired renal function.

The low molecular weight protein cystatin C produced by all nucleated cells and eliminated by glomerular filtration is of special benefit as a marker of renal function. A study was therefore undertaken to investigate whether serum cystatin C could be used as a marker to identify patients with moderately impaired renal function. A cross-sectional descriptive hospital based study was carried out and serum cystatin C was measured in fifty subjects aged 12 to 74 years with a 24 hr creatinine clearance estimation done at the same time. The gold standard creatinine clearance was used to compare the predicted glomerular filtration rate measured using serum cystatin C. Predicted glomerular filtration rate gave a sensitivity of 82% and specificity of 68% with a diagnostic cut-off value of 1.25mg/L cystatin C for identification of patients with moderately impaired renal function with a single random blood sample.