title: Estimated GFR associates with cardiovascular risk factors independently of measured GFR.
abstract: Estimation of the GFR (eGFR) using creatinine- or cystatin C-based equations is imperfect, especially when the true GFR is normal or near-normal. Modest reductions in eGFR from the normal range variably predict cardiovascular morbidity. If eGFR associates not only with measured GFR (mGFR) but also with cardiovascular risk factors, the effects of these non-GFR-related factors might bias the association between eGFR and outcome. To investigate these potential non-GFR-related associations between eGFR and cardiovascular risk factors, we measured GFR by iohexol clearance in a sample from the general population (age 50 to 62 years) without known cardiovascular disease, diabetes, or kidney disease. Even after adjustment for mGFR, eGFR associated with traditional cardiovascular risk factors in multiple regression analyses. More risk factors influenced cystatin C-based eGFR than creatinine-based eGFR, adjusted for mGFR, and some of the risk factors exhibited nonlinear effects in generalized additive models (P<0.05). These results suggest that eGFR, calculated using standard creatinine- or cystatin C-based equations, partially depends on factors other than the true GFR. Thus, estimates of cardiovascular risk associated with small changes in eGFR must be interpreted with caution.
authors: Section of Nephrology, Division of Internal Medicine, University Hospital of North Norway, N-9038 Tromsø, Norway. ulla.dorte.mathisen@unn.no
authors: Ulla Dorte
authors: UD
authors: Mathisen
authors: Toralf
authors: T
authors: Melsom
authors: Ole C
authors: OC
authors: Ingebretsen
authors: Trond
authors: T
authors: Jenssen
authors: Inger
authors: I
authors: Njølstad
authors: Marit D
authors: MD
authors: Solbu
authors: Ingrid
authors: I
authors: Toft
authors: Bjørn O
authors: BO
authors: Eriksen
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002318:Cardiovascular Diseases / Q000209:etiology*; D003404:Creatinine / Q000097:blood*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007472:Iohexol / Q000378:metabolism; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012907:Smoking / Q000503:physiopathology
chemical_list: D055316:Cystatin C; D007472:Iohexol; D003404:Creatinine