Contrast-induced nephropathy: controlled study by differential GFR measurement in hospitalized patients

Background: Without appropriate control measures, contrast-induced nephropathy (CIN) incidence has been claimed to be overestimated. Purpose: To evaluate the relationship and the difference between differential serum creatinine (DsCr), which is currently surrogating as a marker of GIN, and measured differential GFR values as a control measure (DGFR) in hospitalized patients. Material and Methods: GFR was measured two times by Tc-99m DTPA, before and 48 h after contrast media (CM), along with sCr and BUN in 35 inpatients (22 men, 13 women, mean age +/- SD = 61 +/- 14) with no known chronic kidney disease. Results: Relationship was moderate between GFR and sCr (R = 0.50, P < 0.01) in the study population. Pre-CM vs. post-CM values of GFR, sCr and BUN were not statistically different as (mean +/- SD); 78 +/- 36 vs. 73 +/- 35 mL/min/1.73m(2), 0.95 +/- 0.26 vs. 0.94 +/- 0.26 mg/dl and 21 +/- 16 vs. 19 +/- 13 mg/dl, respectively, in the study group. According to basal GFR values, 14 patients (40%) seemed carrying risk of GIN (GFR < 60 mymin/1.73m2) in whom only two had sCr >1.5 mg/dl. Twenty-five patients (71%) had discordant results in relation to Ds Cr and DGFR and two of them had GIN according to classical definition of Ds Cr, although having basal sCr <1.1 mg/dl. Yet, both had low, but stable GFR values. None of patient from the study group underwent hemodialysis. Conclusion: Significant discordance was observed between differential serum creatinine and measured differential GFR in hospitalized patients, suggesting that GIN incidence calculations only based on hospital registry may carry risk of error.