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Cystatin C with Glomerular Filtration Rate, Estimated (eGFR)

Cystatin C with Glomerular Filtration Rate, Estimated (eGFR)

Interpretive Guide

Cystatin C with Glomerular Filtration Rate, Estimated (eGFR)

Clinical Use

Detect chronic kidney disease (CKD) in adults

Monitor CKD therapy and/or progression in adults

Interpretative Information

Prognosis of Chronic Kidney Disease Based on eGFR Valuesa

eGFR,
mL/min/1.73 m2

Prognosis

≥90b

Normal

60-89b

Mild decrease

45-59

Mild to moderate decrease

30-44

Moderate to severe decrease

15-29

Severe decrease

<15

Kidney failure

eGFR, estimated glomerular filtration rate.

a

Data are from Kidney Inter Suppl. 2013;3:1-150. This table applies to creatinine-based and cystatin C-based eGFR.

b

The National Kidney Disease Education Program (NKDEP) recommends that actual values above 60 mL/min/1.73 m2 be reported only as >60 due to variability near the upper limit of the reference range.

Clinical Background

Cystatin C is a low molecular weight (13,359 Da) protein belonging to the superfamily of cystine protease inhibitors. It is produced by all nucleated cells at a reasonably constant rate; production is minimally affected by diet, inflammatory states, lean body mass, or circadian rhythm. Like creatinine, cystatin C is freely filtered by the glomeruli. It is reabsorbed and metabolized by renal tubular cells and does not appear in urine. Tan et al (Diabetes Care. 2002;25:2004-2009) showed serum cystatin C has good correlation with creatinine clearance (ρ = 0.74) and iohexol clearance (ρ = -0.80) and is a useful marker of renal dysfunction in diabetic patients with minimal tubular reabsorption. Cystatin C is used as an alternate marker of glomerular filtration because creatinine production is relatively variable.

The Kidney Disease Improving Global Outcomes (KDIGO) 2012 international guideline recommends using creatinine for initial estimation of glomerular filtration rate (eGFR) (Kidney Inter Suppl. 2013;3:1-150). In people with creatinine-based eGFR 45-59 mL/min/1.73 m2 and no albuminuria, the guideline recommends using cystatin C-based eGFR or creatinine plus cystatin C-based eGFR for confirmation of CKD. An eGFR of <60 mL/min/1.73 m2 in either case confirms a diagnosis of CKD.

Method

Particle-enhanced turbidimetric immunoassay (PETIA)

Analytical sensitivity: 0.25 mg/L

Reportable range: 0.25 mg/L-7.00 mg/L

 

 

 Content reviewed 08/2017

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