Risk Score Predicts Contrast Nephropathy

BY Mitchel L. Zoler

PONTE VEDRA BEACH, FLA. -- An 11-point risk-scoring system can stratify the risk that patients face from contrast-induced nephropathy, based on a validation study that involved more than 3,000 patients.

Applying the risk score in routine practice could identify at-risk patients who should receive a limited amount of contrast during angiography or a percutaneous coronary intervention. It could also identify patients who should receive more intensive prophylaxis before having radiocontrast, Kimberly A. Skelding, M.D., said at the annual meeting of the Society for Cardiovascular Angiography and Interventions.

The risk score was introduced last year (Am. J. Cardiol. 2004;93:1515-9). Scoring uses eight elements, and a patient can receive 0-11 points. The patient scores 2 points if any of the following three features occurs: a baseline creatinine clearance rate of less than 60 mL/min, use of an intraaortic balloon pump during the coronary procedure, and an urgent or emergency coronary procedure. Five other features score 1 point each when present: diabetes, heart failure, hypertension, peripheral vascular disease, and treatment with 260 mL or more contrast during the procedure.

The scoring system was derived from observations made in more than 10,000 patients and was initially verified with a second group of nearly 10,000 patients. The original report found that patients could be divided into four risk groups: low, with 0-4 points; moderate, with 5-6 points; high, with 7-8 points; and very high, with 9 or more points.

The new validation cohort review by Dr. Skelding and her associates included patients who underwent coronary interventions at St. Mary's Hospital in Rochester, Minn., during 2000-2003. This group included 3,213 patients with baseline data and follow-up that were complete enough to allow analysis.

The rates of contrast-induced nephropathy (CIN) and in-hospital mortality were closely linked with risk score in this new cohort. Patients who scored 0-4 points had a 0.2% incidence of nephropathy during follow-up and a 0.5% rate of in-hospital death. Patients with a score of 5-6 had a 2.6% nephropathy rate and a 2.0% mortality rate. Patients with 7-8 points had an 8.2% nephropathy rate and an 8.4% mortality rate. Those with 9-11 points had a 17.3% nephropathy rate and a 25.4% mortality rate, reported Dr. Skelding, a cardiologist at the Mayo Clinic in Rochester, Minn.

This analysis also highlighted the poor prognosis that patients face once they develop CIN. In-hospital mortality occurred in 6.6% of patients who developed CIN, compared with a 1.2% rate in those who did not develop nephropathy. Patients with CIN were 5.3-fold more likely to die in the hospital, compared with those without CIN, a statistically significant difference.

In addition to having a prognostic role, the risk score can guide patient management. Patients with a high score before the procedure should first receive a 12-hour infusion with normal saline, instead of the normal 3 hours, to help prevent CIN, Dr. Skelding said in an interview with this newspaper.