The meteoric rise of noncontrast head CT in emergency settings is not explained by the conspicuous proliferation of nurse practitioners and physician assistants in the ED.

The researchers who expected to find such a connection can’t be faulted for testing the hypothesis. Noncontrast head CT utilization spiked more than 500% between 1994 and 2015, while NPs and PAs saw only 1% of ED patients in 1995 but were closing in on 6% as far back as 2009.

What’s more, a recent Medicare database analysis “demonstrated that NP/PAs order significantly more imaging studies in the outpatient clinic environment compared to primary care physicians for both new and established patients,” the researchers point out in introducing their study, which Academic Radiology published online May 30.  

To see if this effect carried over to ED-based noncontrast head CT, the team, led by Debayan Bhaumik, MD, and Andrew Callen, MD, of the University of Colorado reviewed the records of more than 6,600 patients who underwent the exam at their institution over a seven-year period.

They recorded rates of positive findings, which would tend to indicate appropriate use of the imaging exam in question, along with the training and experience span of ordering clinicians and numerous additional attributes of patients and ED providers.

Defining exam positivity as “any intracranial abnormality necessitating a change in acute management”—e.g., acute hemorrhage, hydrocephalus, herniation, worsening prior findings—the team found 4.6% of physician-ordered exams came back positive vs. 3.76% of NP/PA-ordered exams.

However, the differences were not statistically significant, and increasing provider experience was not associated with positivity, Bhaumik and co-authors report.