How Should We Interpret Differences Between Cystatin C–Based and Creatinine-Based GFR Estimates?

For some patients, cystatin C–based estimates of glomerular filtration rate (eGFR) are considered more accurate than creatinine-based estimates. Two new studies suggest that the difference between these two estimates has prognostic importance.

One study involved 159,000 mostly middle-aged and older residents of Stockholm, Sweden, who had contemporaneous measurements of serum creatinine and cystatin C. Cystatin-based eGFR was lower than creatinine-based eGFR in about half of participants. During median follow-up of 5 years, people in the quartile with the largest negative difference (cystatin-based eGFR >27% lower than creatinine-based eGFR) had significantly higher risks for death (hazard ratio, 2.6), need for renal replacement therapy (HR, …