Patient-reported risk factors increase unnecessary testing before contrast-enhanced CT
New research suggests that when patients report their risk factors for kidney injury prior to contrast-enhanced CT, they are often unnecessarily subjected to additional testing.
Individuals who indicate they are at an increased risk of kidney disease or damage often have their renal function checked by blood testing before undergoing imaging exams involving iodinated contrast, as it can temporarily decrease kidney function. But a study published in the American Journal of Roentgenology reveals that although self-reported risk factors increase screening rates, they do not yield increased instances of renal insufficiency.
“Controversy has existed around optimal strategies for identifying patients at risk for contrast-induced acute kidney injury, and determining in which patients contrast media should be given and in which patients it should be withheld,” corresponding author Daniel I. Glazer, MD, from the Department of Radiology at Brigham and Women’s Hospital, Harvard Medical School, and co-authors explained. “While it is now a standard practice to screen for risk factors to select patients for estimated glomerular filtration rate (eGFR) testing before CT examinations, approaches for such screening vary widely in terms of the specific risk factors used for screening.”
In 2020, the ACR and National Kidney Foundation (ACR/NKF) released a joint consensus statement to standardize practices pertaining to iodinated contrast administration in patients with kidney disease. The statement suggested mandatory screening of patients for a personal history of kidney disease and leaving diabetes mellitus screening optional. Only those who report a history of kidney disease would be subject to eGFR testing, with the cutoff level being 30 mL/min.
Since it has not yet been widely studied, experts sought to evaluate the impact of these screening recommendations. Researchers compared previous self-reported risk factors (presence of dialysis, cancer-treating medications, kidney disease, prior kidney surgery, diabetes mellitus treated with medication, hypertension treated with medication, and multiple myeloma) to the risk factors included in the ACR/NKF recommendations to measure their yield for identifying low eGFR. Patients with any risk factors were required to complete eGFR testing before their CT scan.
Same day eGFR testing revealed that out of 10,256 patients who had these labs, only 1.4% displayed levels below the recommended cutoff. The only significant independent predictors of low eGFR were dialysis, kidney disease and diabetes mellitus treated with medication. If the ACR/NKF criteria had been applied as the trigger for eGFR testing, 89.6% fewer patients would have required testing. This would have increased the yield to 7.1%, but also would have missed 47.2% of patients with low eGFR.
“An optimal strategy may be to limit triggers for eGFR testing to a history of kidney disease or diabetes mellitus treated with medication, as assessing renal function in patients with other risk factors including hypertension, kidney surgery, age ≥60, multiple myeloma, or receiving cancer-treating medications likely leads to substantially increased unnecessary eGFR testing with limited overall benefit,” the authors concluded.
More on contrast studies:
FDA issues safety warning for iodinated contrast media use in children
Research advocates for the return of positive oral contrast in abdominopelvic CT exams
Simple, proven strategies to reduce extravasation of contrast media during CT scans
Allergic reactions to iodinated CT contrast increase likelihood of sensitivity to GBCAs
New scoring system spots patients at risk of contrast-associated kidney injury
In addition to her background in journalism, Hannah also has patient-facing experience in clinical settings, having spent more than 12 years working as a registered rad tech. She began covering the medical imaging industry for Innovate Healthcare in 2021.