The changing definition of contrast-induced nephropathy and its clinical implications: insights from the Blue Cross Blue Shield of Michigan Cardiovascular Consortium (BMC2).

BACKGROUND: The traditional definition of contrast-induced nephropathy (CIN) has been an absolute rise of serum creatinine (Cr) of ≥0.5 mg/dL, although most recent clinical trials have included a ≥25% increase from baseline Cr. The clinical implication of this definition change remains unknown. METHODS AND
RESULTS: We compared the association of the two definitions with risk of death or need for dialysis among 58,957 patients undergoing percutaneous coronary intervention in 2007 to 2008 in a large collaborative registry. Patients with a preexisting history of renal failure requiring dialysis were excluded. Contrast-induced nephropathy as defined by a rise in Cr ≥0.5 mg/dL (CIN(Traditional)) developed in 1,601, whereas CIN defined either as Cr ≥0.5 mg/dL or ≥25% increase in baseline Cr (CIN(New)) developed in 4,308 patients. Patients meeting the definition of CIN(New) but not CIN(Traditional) were classified as CIN(Incremental) (n = 2,707). Compared with CIN(New), CIN(Traditional) was more commonly seen in patients with abnormal renal function, which was more likely to develop in patients with normal renal function at baseline. Compared with CIN(Incremental), patients meeting the definition of CIN(Traditional) were more likely to die (16.7% vs 1.7%) and require in-hospital dialysis (9.8% vs 0%).
CONCLUSIONS: Our data suggest that the traditional definition of CIN (a rise in Cr of ≥0.5 mg/dL) in patients undergoing PCI is superior to ≥25% increase in Cr at identifying patients at greater risk for adverse renal and cardiac events.