A comparison of diagnostic imaging ordering patterns between nurse practitioners and primary care physicians: The right care by the right clinician

Research Objective:

Expanding the use of nurse practitioners (NP) may alleviate a portion of the primary care physician (PCP) shortage. Previous study has found that advanced practice clinicians are associated with more imaging ordering than PCPs under broad patient clinical profiles. This study compares diagnostic imaging ordering between NPs and PCPs under either common or specialized conditions of the patient population.

Study Design:

We employ multivariate logistic regression on retrospective Medicare claims data to estimate the rate of image ordering between NPs and PCPs, adjusting for geography, patient demographics, and comorbidity scores. We use multiple definitions of the most and less frequent conditions, as well as a Herfindahl index measuring the degree of specialization for each provider using each ICD-9 code’s share of all clinical conditions seen by the provider.

Principal Findings:

There were no significant differences between NP and PCP imaging orders for the most frequent clinical conditions regardless of definition used.  Examining the 25% least frequent ICD-9 codes, the odds was significantly higher for NPs than PCPs (OR=1.92; 95% CI: 1.07, 3.43). Similar results were found in other measures of least frequent conditions. After adjusting for the Herfindahl index for clinical specialization of each provider’s patient population, there were no significant differences between NP and PCP imaging orders.  All providers order more images in less clinically specialized patient populations (OR=1.30; 1.25, 1.37).

Conclusion:

NPs order images similarly to PCPs except when seeing patients exhibiting relatively uncommon conditions. Moreover, NPs seeing more clinically specialized patient populations also order significantly fewer images.