Discrepant glomerular filtration rate trends from creatinine and cystatin C in patients with chronic kidney disease: results from the KNOW-CKD cohort

BACKGROUND: Serum creatinine (Cr) and cystatin C (CysC) can both be used to estimate glomerular filtration rate (eGFR(Cr) and eGFR(CysC)). However, certain conditions may cause discrepancies between eGFR trends from Cr and CysC, and these remain undetermined in patients with chronic kidney disease (CKD). METHODS: A total of 1069 patients from the Korean CKD cohort (KNOW-CKD), which enrolls pre-dialytic CKD patients, whose Cr and CysC had been followed for more than 4 years were included in the sample. We performed trajectory analysis using latent class mixed modeling and identified members of the discrepancy group when patient trends between eGFR(Cr) and eGFR(CysC) differed. Multivariate logistic analyses with Firth’s penalized likelihood regression models were performed to identify conditions related to the discrepancy. RESULTS: Trajectory patterns of eGFR(Cr) were classified into three groups: two groups with stable eGFR(Cr) (stable with high eGFR(Cr) and stable with low eGFR(Cr)) and one group with decreasing eGFR(Cr). Trajectory analysis of eGFR(CysC) also showed similar patterns, comprising two groups with stable eGFR(CysC) and one group with decreasing eGFR(CysC). Patients in the discrepancy group (decreasing eGFR(Cr) but stable & low eGFR(CysC); n = 55) were younger and had greater proteinuria values than the agreement group (stable & low eGFR(Cr) and eGFR(CysC); n = 706), differences that remained consistent irrespective of the measurement period (4 or 5 years). CONCLUSIONS: In the present study, we identify conditions related to discrepant trends of eGFR(Cr) and eGFR(CysC). Clinicians should remain aware of such potential discrepancies when tracing both Cr and CysC.