Disparities exist in the utilization of imaging for acute ischemic stroke based on the insurance status of the patient, though the underlying causes of these disparities aren’t quite clear, according to a study published in the August issue of American Journal of Roentgenology.

Specifically, private insurance patients are more likely to receive noninvasive head and neck angiography, head MRI and echocardiography compared to patients with public insurance or the uninsured, explained Waleed Brinjikji, MD, of the department of radiology at the Mayo Clinic in Rochester, Minn., and colleagues.

“These findings are important because disparities in the utilization of diagnostic imaging for patients requiring hospitalization for acute ischemic stroke could potentially lead to differences in treatment options and, most importantly, outcomes,” they wrote.

Brinjikji and colleagues mined the Perspective database, a large administrative database, for inpatients with a primary diagnosis of acute ischemic stroke from November 2005 through December 2011, identifying a total of 210,212 patients. Of these, 5 percent were uninsured, 6.8 percent had Medicaid, 72.9 percent had Medicare and 15.4 percent had private insurance.

Compared with privately insured patients, uninsured patients had significantly lower odds of noninvasive head angiography, neck angiography and head MRI, with odds ratios of 0.78, 0.79 and 0.77, respectively. Medicaid and Medicare patients had similar disparities compared with the privately insured. Medicare and Medicaid patients also were significantly less likely to receive carotid ultrasound.

For some imaging, though, the playing field was more level. Perfusion CT was performed at a similar rate in uninsured and Medicaid patients as it was in the privately insured, and was actually performed at a higher rate in Medicare patients. “The lack of perfusion CT disparities between private insurance patients and Medicaid and uninsured patients is likely because this examination is performed emergently for triage purposes without consideration of insurance status,” wrote the authors.

In speculating about the underlying causes of these disparities, Brinjikji and colleagues suggested that low-income and marginalized populations who are less likely to be privately insured more often seek care at low-volume hospitals where financial pressures may disincentivize expensive imaging. Another factor could be that insurance status is a predictor of stroke symptom recognition.

“In that respect, it is plausible that impaired recognition of stroke symptoms and longer course before hospitalization among low-income populations, those most likely to be uninsured or to have insurance through public sources, may delay presentation and thus decrease the likelihood that these patients present during the temporal window when imaging studies are indicated,” wrote Brinjikji and colleagues. They added that more research is needed to better understand these underlying causes.