Background:
Despite poor sensitivity in acutely ill patients, serum creatinine (and estimated glomerular filtration rate [eGFR
SCR
]) remains the sole means of risk-stratifying patients for acute kidney injury (AKI) prior to contrast-enhanced CT imaging (CECT).
Hypothesis:
We hypothesized that an acute phase marker of renal dysfunction, cystatin-C (expressed as eGFR
CYS
), would more accurately predict contrast-induced nephropathy (CIN) than eGFR
SCR
. Given the risk of arterial vascular events subsequent to AKI, we also evaluated eGFR
CYS
in risk-stratifying patients for major adverse events (MAE) within 1 year of CECT.
Methods:
We followed 462 consecutive adults, without end-stage renal disease, undergoing CECT (any indication) in the outpatient, emergency care setting for CIN and 1-year MAE: death, renal failure, myocardial infarction, stroke, and/or peripheral vascular event requiring intervention (blinded, adjudicated outcome). We excluded patients with life-threatening CECT indications and collected serum for eGFR
SCR
and eGFR
CYS
prior to CECT. Predictive accuracy was defined as the area under the receiver operating characteristic curve (AUROC) and likelihood ratios (LR+ and LR-). A threshold of ≤60 ml/min/m
2
defined an abnormal eGFR
SCR
or eGFR
CYS
.
Results:
CIN occurred in 14% and a MAE in 17% (low observer variability, κ>0.9) of our heterogeneous population: mean age 50 yrs (±16 yrs), 51% discharged after CECT, 16% with diabetes mellitus (DM), and only 16% with eGFR
SCR
≤60ml/min/m
2
. CIN was associated with 1-year MAE: RR 2.4 (1.5-4.0) after adjusting for age and existing co-morbidities (active malignancy, CHF, DM, and CAD). The AUROC, LR+ and LR- for eGFR
SCR
were 0.55 (0.47-0.63), 0.9 (0.4-2.1) and 1.0 (0.9-1.1). In comparison, the AUROC, LR+, and LR- for eGFR
CYS
were 0.79 (0.62-0.96), 5.5 (3.9-7.6) and 0.43 (0.31-0.57), respectively. The MAE rate did not differ in patients with normal (13%) or abnormal (15%, p=0.5) pre-CECT eGFR
SCR
. Whereas, an abnormal eGFR
SCR
was associated with a 29% (p<0.01) increase in MAE.
Conclusions:
In patients undergoing CECT in the outpatient setting, eGFR
CYS
more accurately predicted CIN and more effectively risk-stratified patients for 1-year MAE than eGFR
SCR
. These findings warrant prospective validation.
Intravenous iodinated contrast is not associated with acute kidney injury in adult patients with nephrotic syndrome
