PLASMA CYSTATIN-C AS A MARKER IN CHRONIC Rt.NAlDISEASE ... •

Abstract

The objective of the present study is to learn the truth about the value of serum cystatin C as a marker for glomerular function and whether or not it is better than serum creatinine (SCr) as has been postulated by other studies. This study included 68 subjects with various renal diseases and 31 matched healthy volunteers. Patients with renal diseases were divided into 3 groups according to their creatinine clearance values: Group A included 23 patients having a clearance rate of :::30 mL/min/1.73 m2• Group B included 24 patients whose clearance rate was >30 :"::70 mL/min/1.73 m2 . Group C included 21 patients with clearance rate >70 mL/min/1.73 m2 • The recorded median values of SCr and cystatin-C in healthy volunteers were 0.85 mg/dL and 0.51 mg/L, respectively. Patients with clearance rate go mL/min/1.73 m2 (groups A and B) had SCr and cystatin-C median values of 2.40 mg/dL and 2.28 mg/L, respectively. Group A patients had median values of3.40 mg/dL and 2.97 mg/L for SCr and cystatin-C, respectively. Group B patients had a median value of 1.40 mg/dL for SCr and 1.55 mg/L for cystatin-C. Group C patients had a median SCr value of 0.80 mg/dL and a median value of0.50 mg/L for cystatin-C. Comparison between the three groups of patients with renal disease showed that there was a great statistical significant difference as regards their SCr and cystatin-C were p was <0.001 for both parameters, respectively. Moreover, both markers were significantly higher in group A patients when compared tci group B patients (p<0.001). Similar results were obtained when comparing SCr and cystatin-C in group B and C. Healthy volunteers had significantly lower SCr and cystatin-C when compared with patients in group A and group B where p was <0.001, respectively. On the other hand, these markers had comparable values with those recorded from patients with renal diseases yet still maintaining a clearance rate >70 mL/min/1.73 m2 (group C). ROC plots demonstrated that the best cut-off value for SCr was 0.90 mg/dL which provided a diagnostic sensitivity of91.5% and specificity of90.3%. The best cut-off level for cystatin-C was 0.86 mg/L and. the corresponding diagnostic sensitivity was 91.5% while the specificity was 100%. The AUC for SCr was 0.875 and for cystatin-C was 0.927. It was concluded that the diagnostic efficiency of serum cystatin-C is better than that of SCr.