Cystatin C: efficacy as screening test for reduced glomerular filtration rate

Area of Science:

• Nephrology
• Biomarkers
• Clinical Chemistry

Background:

• Serum cystatin C, a cysteine proteinase inhibitor, is a proposed marker for glomerular filtration rate (GFR).
• Assessing renal function typically involves serum creatinine and creatinine clearance, but their efficacy can be limited.
• Evaluating novel biomarkers like cystatin C is crucial for improving diagnostic accuracy in nephrology.

Purpose of the Study:

• To evaluate the efficacy of serum cystatin C as a screening test for reduced creatinine clearance.
• To compare the diagnostic performance of cystatin C against serum creatinine across the full spectrum of renal function.
• To determine if cystatin C's efficacy differs in glomerular versus tubular renal impairment.

Main Methods:

• Measured serum cystatin C, serum creatinine, and creatinine clearance in 226 patients with diverse nephropathies.
• Analyzed subgroups of patients with glomerular (n=53) and tubular (n=26) impairment.
• Utilized receiver-operating characteristic (ROC) plots to assess diagnostic sensitivity.

Main Results:

• Serum cystatin C demonstrated higher sensitivity (97% vs. 83%) and negative predictive value (96% vs. 87%) in detecting reduced creatinine clearance compared to serum creatinine.
• ROC analysis revealed a significantly higher sensitivity for cystatin C (95%, p < 0.05).
• No significant difference in efficacy was observed between cystatin C and creatinine in subgroups with glomerular or tubular impairment.

Conclusions:

• Serum cystatin C is as efficacious as serum creatinine for detecting reduced GFR.
• Serum cystatin C may offer superior efficacy as a screening test for renal function compared to creatinine.
• The diagnostic performance of cystatin C is independent of the type of renal impairment (glomerular or tubular).