Evaluation of renal function tests by age and sex to determine emergency department patients' eligibility for cardiac computed tomography.

Background: Coronary computed tomography angiography (CCTA) can be used for low-risk chest pain patients, but presents a risk of contrast-induced nephropathy.

Objective: We compared, by age and sex, the percent of patients who would become ineligible for CCTA based on serum creatinine (SCr) and glomerular filtration rate (GFR) cutoff points.

Methods: All adult patients who presented to the Emergency Department (ED) with chest pain were screened using their first ED SCr as part of the ROMICAT (Rule Out Myocardial Infarction Using Computer Assisted Tomography) study. This was a secondary analysis of the screening logs of that study. The Modification of Diet in Renal Disease formula was applied to calculate estimated GFR and the percent of patients, by age and sex, meeting commonly applied exclusion criteria using selected SCr and GFR cutoff values. This was our primary outcome.

Results: Of 2398 patients screened, 384 (16%) were excluded for high-risk features or technical limitations of CCTA, leaving 2014 patients who were studied; 56% were male. For all cutoff points of SCr (≥1.3 mg/dL, ≥1.5 mg/dL, ≥1.8 mg/dL), the percent of males excluded significantly exceeded that of females (p < 0.0001 [28.6% males to 18.5% females]; p < 0.0001 [17.4% males to 11.2% females]; p = 0.0004 [10.1% males to 5.8% females], respectively). Conversely, for two of the three cutoff points of GFR (≤60 mL/min/1.73 m(2) and ≤45 mL/min/1.73 m(2)), the percent of females excluded significantly exceeded that of males (p < 0.0001 [33.6% females to 25.4% males] and p = 0.0015 [17.6% males to 12.5% females], respectively).

Conclusions: The choice of SCr or GFR to screen patients for CCTA selectively excludes either males or females, respectively. Therefore, individual physicians and institutions must understand the impact of both renal function tests and cutoff points when identifying patients who may be eligible for CCTA.