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

Without appropriate control measures, contrast-induced nephropathy (CIN) incidence has been claimed to be overestimated.

To evaluate the relationship and the difference between differential serum creatinine (DsCr), which is currently surrogating as a marker of CIN, and measured differential GFR values as a control measure (DGFR) in hospitalized patients.

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.

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 CIN (GFR < 60 mL/min/1.73m(2)) in whom only two had sCr >1.5 mg/dl. Twenty-five patients (71%) had discordant results in relation to DsCr and DGFR and two of them had CIN according to classical definition of DsCr, 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.

Significant discordance was observed between differential serum creatinine and measured differential GFR in hospitalized patients, suggesting that CIN incidence calculations only based on hospital registry may carry risk of error.