Study of Serum Cystatin C and Serum Creatinine in Different Stages of Chronic Kidney Disease Patients.

There is lack of consistent surrogate markers of kidney function to identify established disease, especially in early stages of CKD. Creatinine remains within normal levels until a significant reduction in renal function has occured. Cystatin C appears to be unaffected by muscle mass, diet, or gender. Its clearance is only by glomerular filtration. The plasma concentration is not influenced by inflammation or liver disease. It is not affected by optical interferences. Considering these benefits, it is more useful when trying to detect mild to moderate impairment of kidney function.

MATERIAL: An observational, analytical study was conducted over a duration of 18 months. The study participants were divided into 2 groups based on eGFR.

OBSERVATION: 67.5% patients had raised Cystatin C as compared to only 12.5% who had raised Creatinine. In our study, we found that Serum Creatinine (r=-0.85, p< 0.001) was better than Cystatin C (r=-0.55, p< 0.001) in all stages of CKD. However, in patients with eGFR ≥ 60 ml/min/m2. Cystatin C (r = -0.68, p<0.001) was a more sensitive marker to detect renal dysfunction at an early stage as compared to Serum Creatinine (r = -0.48, p<0.001). Overall, the AUC (Area Under the Curve) for Serum Creatinine is more than Cystatin C. However, in patients with eGFR≥ 60ml/ min/1.73m2, AUC for cystatin C is more. Thus, Cystatin C is more sensitive than Serum Creatinine to detect early renal dysfunction.

CONCLUSION: We found out that both serum creatinine and serum cystatin C were significantly increased across CKD groups but cystatin C is a better predictor of CKD than creatinine in stages with eGFR≥60 ml/min/1.73 m2 as serum cystatin C was found to be raised contrary to serum creatinine which was within normal limits, although in stages with eGFR<60 ml/min/1.73 m2 there was no significant difference between the two. We found out that normal serum creatinine levels during the stage of kidney disease with eGFR≥60 ml/min/1.73 m2 does not necessarily mean normal renal function. Cystatin C should be encouraged as a screening tool for early renal impairment in the patient as the risk of developing CKD, especially in long-standing hypertensive and diabetic patients as an adjunct to creatinine estimation. It should also be included in the management protocol for these patients.