IV radiocontrast use in CT pulmonary angiography (CTPA) does not appear to be associated with kidney impairment, according to a recent analysis of ED patients.
Researchers in Canada performed a cohort study in adult patients presenting to the ED who had D-dimer testing between 2013 and 2018. They used a fuzzy regression discontinuity design based on the fact that patients just above or below the typical 500 ng/mL eligibility cutoff for CTPA have different probabilities of contrast exposure but otherwise should have similar potential confounders. The study's main outcome measure was estimated glomerular filtration rate (eGFR) for up to six months after the index ED visit. The results were published April 5 by JAMA Internal Medicine.
Overall, 156,028 patients received a D-dimer test over the study period. Mean age was 53 years, 87,822 (56%) were women, and the mean eGFR level at baseline was 86 mL/min/1.73 m2. No association of contrast with eGFR was seen for up to six months; the mean change in eGFR associated with CTPA exposure was −0.4 mL/min/1.73 m2 (95% CI, −4.9 to 4.0 mL/min/1.73 m2). In addition, no association was seen between CTPA exposure and need for kidney replacement therapy (risk difference [RD], 0.07%; 95% CI, −0.47% to 0.61%), death (RD, 0.3%; 95% CI, −2.9% to 3.2%), or, although some data were missing, acute kidney injury (RD, 4.3%; 95% CI, −2.7% to 12.9%). CTPA exposure appeared to be associated with harm in patients with diabetes (mean eGFR change, −6.4 mL/min/1.73 m2; 95% CI, −15.4 to 0.2 mL/min/1.73 m2) but not in those with other risk factors for contrast-induced nephropathy, although this subgroup analysis was underpowered.
The authors noted that the generalizability of their results is limited but said they found no evidence that IV contrast for CTPA in an emergency setting has a harmful effect on kidney function. “Definitively proving a negative is difficult, but the results of our study suggest that a clinically significant association of intravenous contrast with long-term renal function is very unlikely,” they wrote. They suggested further, more robust research among patients with diabetes, since subgroup analysis suggested a higher risk for harm.
An accompanying editorial noted that because of the study design, the use of IV contrast was “effectively randomized” among patients close to the D-dimer cutoff threshold. “These findings add considerably to our understanding of the safety of newer contrast agents, which has otherwise been based on hard-to-interpret results from observational comparisons subject to selection bias,” the editorialists wrote. They concluded that the study authors “provide an imaginative and elegant application—one to learn from in the pursuit of evidence-based medicine with observational research methods.”
An article in the March 2020 ACP Hospitalist reviewed evidence and expert opinions on IV contrast and acute kidney injury.