PT - JOURNAL ARTICLE AU - Fleming, Susannah AU - Perera-Salazar, Rafael AU - Taylor, Kathryn S AU - Jones, Louise AU - Hobbs, FD Richard AU - James, Tim AU - O’Callaghan, Chris A AU - Shine, Brian AU - Verbakel, Jan Y AU - Stevens, Richard AU - Bankhead, Clare TI - Frequency of Renal Monitoring — Creatinine and Cystatin C (FORM-2C): an observational cohort study of patients with reduced eGFR in primary care AID - 10.3399/BJGP.2020.0940 DP - 2021 Sep 01 TA - British Journal of General Practice PG - e677--e684 VI - 71 IP - 710 4099 - http://bjgp.org/content/71/710/e677.short 4100 - http://bjgp.org/content/71/710/e677.full SO - Br J Gen Pract2021 Sep 01; 71 AB - Background Monitoring is the mainstay of chronic kidney disease management in primary care; however, there is little evidence about the best way to do this.Aim To compare the effectiveness of estimated glomerular filtration rate (eGFR) derived from serum creatinine and serum cystatin C to predict renal function decline among those with a recent eGFR of 30–89 ml/min/1.73 m2.Design and setting Observational cohort study in UK primary care.Method Serum creatinine and serum cystatin C were both measured at seven study visits over 2 years in 750 patients aged ≥18 years with an eGFR of 30–89 ml/min/1.73 m2 within the previous year. The primary outcome was change in eGFR derived from serum creatinine or serum cystatin C between 6 and 24 months.Results Average change in eGFR was 0.51 ml/min/1.73 m2/year when estimated by serum creatinine and −2.35 ml/min/1.73 m2/year when estimated by serum cystatin C. The c-statistic for predicting renal decline using serum creatininederived eGFR was 0.495 (95% confidence interval [CI] = 0.471 to 0.519). The equivalent c-statistic using serum cystatin C-derived eGFR was 0.497 (95% CI = 0.468 to 0.525). Similar results were obtained when restricting analyses to those aged ≥75 or <75 years, or with eGFR ≥60 ml/min/1.73 m2. In those with eGFR <60 ml/min/1.73 m2, serum cystatin C-derived eGFR was more predictive than serum creatinine-derived eGFR for future decline in kidney function.Conclusion In the primary analysis neither eGFR estimated from serum creatinine nor from serum cystatin C predicted future change in kidney function, partly due to small changes during 2 years. In some secondary analyses there was a suggestion that serum cystatin C was a more useful biomarker to estimate eGFR, especially in those with a baseline eGFR <60 ml/min/1.73 m2.