Kathleen Louden

November 10, 2015

CHICAGO — Nurses do not order diagnostic imaging tests any more frequently than primary care physicians, according to a study of Medicare patients.

In fact, the only time nurse practitioners were more likely to order diagnostic imaging than primary care physicians was when the patient's diagnostic code was uncommon, said lead investigator Miao Jiang, PhD, a research fellow at the Harvey L. Neiman Health Policy Institute in Reston, Virginia.

"The primary care physician shortage is becomingly increasingly important, and one solution is to use nurse practitioners," Dr Jiang told Medscape Medical News.

It is expected that by 2025, there will be a shortage of 12,500 to 31,100 primary care physicians, according to a report from the American Academy of Medical Colleges.

Nurses could help fill this gap, and one study has shown that nurses provide equal or better-quality care at a lower cost than other healthcare professionals (J Am Acad Nurse Pract. 2010;22:228-231).

However, in another study, which Dr Jiang and some of her colleagues were involved in, nurse practitioners and physician assistants ordered more imaging services than primary care physicians (JAMA Intern Med. 2015;175:101-107), as reported by Medscape Medical News.

In their current analysis, presented here at the American Public Health Association 2015 Annual Meeting, Dr Jiang's team analyzed Medicare claims data for 661,543 visits.

The sample involved Medicare beneficiaries 66 years and older who had an evaluation and management visit in 2011 or 2012. Patients were seen by 92,579 primary care physicians and 13,410 nurses. Doctors ordered 623,515 imaging tests and nurses ordered 38,028.

Diagnostic imaging orders placed within 30 days of the index visit were included in the analysis, but all mammograms were excluded. Multivariate logistic regression modeling was adjusted for patient age, sex, race, geographic region, and comorbidities.

The researchers used International Classification of Diseases, Ninth Revision (ICD-9) codes to evaluate how common a condition was.

Hypertension, Back Pain, Diabetes

Hypertension, back pain, and diabetes were among the most common conditions found in the claims data, and nephritis, head and neck cancer, and urinary calculi were among the least common.

When the patient's condition was common — in the top 0.5% to 10.0% of ICD-9 codes — both nurse practitioners and primary care physicians tended to order fewer imaging tests, and there was no significant difference between type of provider.

However, when the patient's condition was uncommon — in the bottom 25% of ICD-9 codes — there was a "huge difference" in imaging ordering practices, Dr Jiang reported. Nurses were nearly twice as likely as primary care physicians to order diagnostic imaging tests (odds ratio [OR], 1.92; 95% confidence interval [CI], 1.07 - 3.43).

There was no significant difference between nurse practitioner and primary care physician orders when the degree of specialization of the providers, measured with the Herfindahl–Hirschman Index, was assessed. All providers who saw clinically specialized patient populations ordered significantly fewer imaging tests, the researchers report.

The overuse of imaging "is a major problem in the United States and is driving up healthcare costs, so this is an interesting study," said Ajit Appari, PhD, from the University of Texas School of Public Health in Houston, who was not involved in the study.

"However, there are many provider variables the authors did not consider that could make a difference in the findings," he told Medscape Medical News.

Dr Appari suggested that the team evaluate differences in imaging ordering by provider age, sex, and years in practice, but Dr Jiang explained that the Medicare dataset does not include the demographic characteristics of the provider.

Both disciplines follow similar national standards of care and approaches to clinical diagnosis.

This study appears to corroborate previous research findings that nurse practitioners and primary care physicians have similar diagnostic workup patterns, said Cindy Cooke, DNP, president of the American Association of Nurse Practitioners.

"The abstract suggests that both disciplines follow similar national standards of care and approaches to clinical diagnosis," Dr Cooke told Medscape Medical News.

The finding that workups are more extensive for uncommon diagnoses is "not unanticipated" because nurse practitioners also practice in specialty settings, she explained. But she pointed out that "this finding was no longer significant after adjustment for the Herfindahl index, which accounted for any possible differences in patient populations between the two provider groups."

Patients in 21 states and the District of Columbia have full, direct access to nurse practitioner services, said Dr Cooke. Those legislative decisions were based on "decades of extensive research and practice outcomes," she explained.

Dr Jiang, Dr Appari, and Dr Cooke have disclosed no relevant financial relationships.

American Public Health Association (APHA) 2015 Annual Meeting: Abstract 321129. Presented November 1, 2015.

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