NPs, PAs Order More Diagnostic Imaging Than Physicians

Diana Phillips

December 03, 2014

Physician assistants and nurse practitioners order diagnostic imaging more frequently than primary care physicians do in the evaluation of similar patients, according to the results of a study published online November 24 in JAMA Internal Medicine. However, not everyone is convinced of the accuracy or importance of the study conclusions.

Specifically, advanced practice clinicians (APCs) ordered imaging for 2.8% of patients after office-based evaluation and management visits compared with 1.9% for primary care physicians (PCPs), report Danny R. Hughes, PhD, research director and senior research fellow of the Neiman Institute, Reston, Virginia, and colleagues.

The small differential in ordering rates is unlikely to have an effect on individual patients but may be more influential at the population level, the authors write. Importantly, they stress, the findings point to the need to carefully evaluate the relative value of expanding the use of APCs as a vehicle for reducing labor costs and addressing PCP shortages.

"While we cannot discern whether the differential in ordering represents overuse by APCs (rather than underuse by PCPs), efforts to expand access to care by simply substituting APCs for physicians without careful imaging appropriateness mechanisms may further elevate health care costs and potentially increase unnecessary radiation exposure," they write.

Using 2010 to 2011 Medicare claims data for a 5% sample of beneficiaries, the investigators compared order practices for episodes of care delivered by APCs and PCPs (identified by provider specialty codes), controlling for geographic variation and patient demographics and comorbidities.

The results showed that APCs ordered 0.3% more images per care episode than the PCPs, after adjusting for patient age group, sex, race, state, urban, and Charlson Comorbidity Index. When considered by imaging type, ACPs ordered 0.3% more radiographs for new patients and 0.2% more for established patients compared with PCPs, after adjusting for the same variables.

ACPs also ordered more advanced imaging studies than PCPs for established patients (0.1%). However, the authors found no difference in advance imaging orders for new patients.

One notable result was a decrease in the number of imaging studies ordered by APCs compared with PCPs for patients with acute respiratory tract infection. "One possible interpretation is that more patients with acute respiratory tract infection are quickly referred to PCPs or specialists who then order necessary imaging," the authors hypothesize. Alternatively, the finding could reflect more rigid protocols and guidelines for APCs for examining these patients, they write.

The variation in ordering patterns may support the use of computerized order entry systems that incorporate integrated clinical decision support. "Although some physicians have described such software tools as 'a nuisance' and 'not relevant,' these tools may have value in normalizing APC ordering behavior to that of physicians," the authors write.

Because there is currently considerable variation in the scope of practice for APCs across the United States, as well as the kinds of tests they are permitted to order, "one way to consider the effects of increasing scope of practice for the ordering of diagnostic tests is to compare the ordering patterns for patients receiving radiography with those receiving nonradiographic tests," the authors suggest.

The increased use of imaging by APCs "may have important ramifications on care and overall costs at the population," the authors write. "This does not mean that APCs cannot serve an important, growing role in primary care access. But any such expansion must be mindful of the additional cost, safety, and quality implications it may incur." Rather than expanding the scope of APC practice alone, greater PCP and APC team coordination "may produce better outcomes," they state.

John McGinnity, PA-C, president of the American Academy of Physician Assistants, questions the validity of the conclusions.

"[Physician assistants] have been proven to improve outcomes for patients, and the profession strongly supports evidence-based use of all diagnostic testing," McGinnity stresses. "One of the investigation's major limitations is the fact that the data set does not identify the medical or surgical specialty in which a PA or NP practices. The authors' comparison of primary care physicians to PAs and NPs from any and every specialty creates a faulty premise on which the whole study stands."

The bottom line, McGinnity notes, "is that team-based care is an effective way to provide access to quality medicine."

The authors and McGinnity have disclosed no relevant financial relationships.

JAMA Intern Med. Published online November 24, 2014. Abstract


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