They finally concluded that the equation using serum cystatin C level alone yields estimates with small biases in age, sex, and race subgroups, which were improved in equations including these variables (24).In a meta-analysis by Zhang et al (25), of 17 studies with 2521 patients with chronic kidney disease, it was demonstrated significant correlations between cystatin C, serum creatinine and GFR. The gene discussed is CST3; the disease is chronic kidney disease.