Discordance between Estimate Glomerular Filtration Rate with Creatinine and Cystatin is Associated with Inflammation and Worsened Survival in Heart Failure

Introduction Glomerular filtration rate (GFR) can be estimated using serum creatinine or cystatin C. At the population level, these equations predict GFR with similar accuracy but can give substantially different results at the level of an individual patient. These within-patient differences may be explained by factors such as inflammation, as cystatin C is associated with higher levels of established inflammatory markers. We sought to determine if the discordance between the two GFR estimates could be attributed to inflammation, and furthermore to examine if this information held prognostic value. Hypothesis Discordance of estimated GFR (eGFR) using creatinine vs. cystatin C will be affected by inflammation and patients with greater discordance will have worsened survival. Methods We analyzed an outpatient cohort of patients with chronic stable heart failure (n= 162). CKDEPI-Creatinine and CKDEPI-Cystatin C equations were used to estimate GFR. Discordance of eGFR was calculated as the ratio of eGFRcreatinine to eGFRcystatin. (values higher than 1 represent eGFRcreatinine > eGFRcystatin and lower than 1 represent eGFRcystatin > eGFRcreatinine). Results In the overall population eGFRcreatinine was 54±28mL/min/m2 and the eGFRcystatin was 43±25mL/min/m2, resulting in an average ratio of 1.3±0.4. There were, however, substantial differences in individual patients with the 10th percentile ratio at 0.9 and 90th percentile a ratio of 1.7. Notably, the ratio was correlated with plasma interleukin-6 (r= 0.24), C-reactive protein (r= 0.23), and ST2 (r= 0.26); p Conclusion The discordance of eGFR with creatinine and cystatin C was associated with markers of inflammation and holds powerful independent prognostic information. Additional study into the drivers of the discordance in GFR estimates by cystatin C and creatinine is warranted.