AbstractDespite standard laboratory quality control, drift and day-to-day variability in cystatin C measurements can be observed. We investigated whether correction for drift and day-to-day variation in cystatin C measurements improves the association of estimated glomerular filtration rate (eGFR) with chronic kidney disease (CKD) risk factors and prognosis.Plasma samples of the PREVEND study (Dutch cohort study, n=8592) were used to measure cystatin C (Gentian assay) on 243 random days. A correction factor was calculated for each measurement day. GFR was estimated with CKD-EPI equation using routinely measured cystatin C (eGFRCompared to non-reclassified participants, participants re-classified upward had significantly lower age, body mass index, blood pressure, cholesterol, glucose and albuminuria, whereas the opposite was true for participants reclassified downward. CKD risk factors explained more variance in eGFRCorrection for drift and day-to-day variation in cystatin C measurement improves eGFR using cystatin C for its association with CKD risk factors and incident cardiovascular events.