Variation in Contrast Volume Evaluated for Association With Acute Kidney Injury
July 10, 2017—Findings from an investigation of the variation in contrast volume and acute kidney injury (AKI) incidence among United States physicians after performing percutaneous coronary intervention (PCI) were published by Amit P. Amin, MD, et al online in Journal of the American Medical Association (JAMA): Cardiology.
In this cross-sectional study involving more than 1.3 million patients who underwent PCI, the investigators observed large variations in the incidence of AKI and in contrast use among physicians who performed the procedures. There was no evidence that physicians used significantly less contrast in patients at higher risk of AKI. The variation among physicians and the absence of an adjustment in contrast volume for patients at higher risk for AKI underscores an important opportunity to reduce AKI, noted the investigators.
As summarized in JAMA: Cardiology, the study investigators used the American College of Cardiology National Cardiovascular Data Registry (NCDR) CathPCI Registry to identify in-hospital care for PCI in the United States. Participants included 1,349,612 patients who underwent PCI performed by 5,973 physicians in 1,338 hospitals between June 1, 2009, and June 30, 2012. Data analysis was performed from July 1, 2014, to August 31, 2016.
The primary outcome was AKI, defined according to the Acute Kidney Injury Network criteria as an absolute increase of ≥ 0.3 mg/dL or a relative increase of ≥ 50% from preprocedural to peak creatinine. A secondary outcome was the mean contrast volume as reported in the NCDR CathPCI Registry. Physicians who performed > 50 PCIs per year were the main exposure variable of interest. Hierarchical regression with adjustment for patients’ AKI risk was used to identify the variation in AKI rates, the variation in contrast use, and the association of contrast volume with patients’ predicted AKI risk.
As summarized in JAMA: Cardiology, of the more than 1.3 million patients who underwent PCI, the mean age was 64.9 years, 908,318 (67.3%) were men, and 441,294 (32.7%) were women. AKI occurred in 94,584 patients (7%).
The investigators reported that a large variation in AKI rates was observed among individual physicians ranging from 0% to 30% (unadjusted), with a mean adjusted 43% excess likelihood of AKI (median odds ratio, 1.43; 95% confidence interval [CI], 1.41–1.44) for statistically identical patients presenting to two random physicians.
In addition, a large variation in physicians’ mean contrast volume, ranging from 79 mL to 487 mL with an intraclass correlation coefficient of 0.23 (interquartile range, 0.21–0.25), was observed, implying a 23% variation in contrast volume among physicians after adjustment. There was a minimal correlation between contrast use and patients’ AKI risk (r = −0.054). Sensitivity analysis after excluding complex cases showed that the physician variation in AKI remained unchanged.
The investigators concluded that AKI rates vary greatly among physicians, who also vary markedly in their use of contrast and do not use substantially less contrast in patients with higher risk for AKI. These findings suggest an important opportunity to reduce AKI by reducing the variation in contrast volumes across physicians and lowering its use in higher-risk patients, stated the investigators in JAMA: Cardiology.