Calculation of glomerular filtration rate expressed in mL/min from plasma cystatin C values in mg/L

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Abstract

The Cockcroft-Gault formula is often used to calculate the glomerular filtration rate (GFR) from plasma creatinine results. In Sweden this calculation is not usually done in the laboratory, but locally in the wards. These manual calculations could cause erroneous results. In several studies plasma cystatin C has been shown to be superior to plasma creatinine for estimation of GFR. One limitation of using cystatin C as a GFR marker is that there is no conversion formula transforming cystatin C expressed as mg/L to GFR expressed as mL/min. In this study plasma creatinine and cystatin C were compared with iohexol clearance. A stronger correlation (p<0.0001) was found between cystatin C and iohexol clearance (r(2) =0.91) than between creatinine and iohexol clearance (r(2) =0.84). From the correlation data a formula was calculated to convert cystatin C expressed as mg/L to GFR (mL/min). The formulas y=77.24x -1.2623 (Dade Behring cystatin C calibration) or y=99.43x -1.5837 (DakoCytomation cystatin C calibration) are used to calculate GFR expressed in mL/min from the cystatin C value in mg/L and both results are reported to the referral doctor. These formulas can provide the clinicians with reliable and readily available GFR data based on single measurements of cystatin C concentrations.

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Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Medicinal Chemistry

Keywords

  • glomerular filtration ratio, creatinine, cystatin C, iohexol, kidney
Original languageEnglish
Pages (from-to)25-30
JournalScandinavian Journal of Clinical & Laboratory Investigation
Volume64
Issue number1
Publication statusPublished - 2004
Publication categoryResearch
Peer-reviewedYes