Changes in serum creatinine level and estimated glomerular filtration rate on the day following cardiac catheterization can predict a patient’s risk of developing contrast-induced nephropathy (CIN), researchers concluded.

The investigators established cut-off values for these changes that could aid in deciding which patients could be discharged without concern about CIN, according to a report published online ahead of print in the Journal of Cardiology.

CIN is defined as a 0.5 mg/dL or greater or 25% or greater increase in serum creatinine (SCr) from baseline 48–72 hours after contrast exposure. “Therefore, CIN cannot be diagnosed on the day of cardiac catheterization or on the following day, when the majority of patients who undergo elective cardiac catheterization are discharged from the hospital in the real-world setting,” the authors pointed out.

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Makoto Watanabe, MD, PhD, of Nara Medical University in Kashihara, Japan, and colleagues studied 860 patients who underwent cardiac catherization. They measured SCr and estimated glomerular filtration rate (eGFR) before catheterization, on the following day, and 48–72 hours after the procedure.

CIN developed in 40 patients. From baseline to the day following the procedure, SCr levels increased significantly from 1.55 to 1.79 mg/dL, but decreased significantly from 1.21 to 1.18 mg/dL in those without CIN. The eGFR decreased significantly from 47.3 to 40.6 mL/min/1.73 m2 in patients with CIN, but increased significantly from 53.1 to 53.6 mL/min/1.73 m2 in those without CIN.

The researchers’ analyses showed that the cut-off value for change in SCr was 0.1 mg/dL, which has a sensitivity and specificity of 72.5% and 86.1%, respectively. The cut-off value for change in eGFR was −1.1 mL/min/1.73 m2, which has a sensitivity and specificity of 85% and 64.9%, respectively. The negative predictive value was high for both cut-off values, according to the investigators. The authors stated that patients with a change in SCr less than 0.1 mg/dL or eGFR less than −1.1 mL/min/1.73 m2 could be discharged from the hospital without concern about CIN.

On multivariate analysis, a 0.1 mg/dL or greater increase in SCr and a 1.1 mL/min/1.73 m2 or greater decrease in eGFR on the day following cardiac catheterization independently predicted CIN. These changes were associated with a significant 29.3 and 69.7 times increased odds of CIN, respectively.

“The present study demonstrates for the first time that the small changes in SCr or eGFR on the day following contrast use can predict subsequent development of CIN,” the authors wrote.

The authors noted that more than 80% of patients with an eGFR below 60 mL/min.1.73 m2 received saline or bicarbonate before and up to several hours after contrast use, but some of them developed CIN, suggesting current methods of hydration cannot completely prevent CIN. “It would be ideal to determine which patients will develop CIN before the procedure and prevent CIN from developing, but such an approach is not realistic. The second best is to diagnose CIN as soon as possible after contrast use. In this context, the new cut-offs for change in SCr and eGFR will help diagnose CIN on the day following the procedure and before hospital discharge.