Editor’s Note: PPP sponsors educational programming for its members and invites all interested parties to take part in our periodic Journal Club. For those new to the format, a journal club is a gathering of medical professionals to discuss a scientific paper. The paper under discussion is distributed prior to the meeting date, so that all participants can read it. The club meeting begins with a member presenting a summary of the chosen paper. Then the discussion begins, including questions about the study design, methods, results, and conclusions. Finally, a consensus is rendered regarding the overall value of the paper.
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February 27, 2020
A Comparison of Diagnostic Imaging Ordering Patterns Between Advanced Practice Clinicians and Primary Care Physicians Following Office-Based Evaluation and Management Visits
Danny R. Hughes, PhD, Miao Jiang, PhD, and Richard Duszak Jr, MD
How do the imaging ordering practices of primary care physicians (PCPs) compare to that of advanced practice clinicians?
The authors begin their article discussing the well-known primary care physician (PCP) shortage and how this has led, in part, to an increase in the scope of practice for non-physician clinicians. While there have been several poorly designed studies surrounding clinical outcomes, there has been much more limited data on the diagnostic imaging, laboratory and referral order practices of non-physicians. This is important since non-physician labor is often touted as being more cost-effective than that of physicians.
The Medicare 5% Limited Data Set (LDS) is a file available through Medicare that is stripped of direct identifies of beneficiaries. It contains a 5% national sample.
The Charlson Comorbidity Index, used in a modified fashion in this study, is a weighted index designed to predict mortality within 1 year of hospitalization. The original index utilized 19 conditions but the authors used a modified score that utilized 17 conditions.
CPT codes for outpatient visits include 99201 through 99205 for new patients and 99211 through 99215 for established patients.
This was a retrospective review of 2010-2011 Medicare fee-for-service claims. The authors utilized the 2010 5% LDS Physician/Supplier Part B claims file to identify patient episodes and the 5% LDS inpatient file to calculate the co-morbidity index. Included patient episodes were those that were in “office” and had a CPT code between 99201 and 99205 or 99211 and 99215. If a visit or imaging event involved more than one type of clinician, it was excluded from the study. It was also excluded if there was a prior claim within the prior 30 days. The primary outcome was whether an imaging event occurred.
Inclusion criteria for patients included beneficiaries 66 years of older in 2011, continuous Medicare Part A and B coverage in 2010 and 2011 with no concurrent health maintenance organization enrollment.
Authors used the Charlson Comorbity Index to aid in the controlling of confounders.
Multivariable logistic regression was used to adjust for confounding factors including age, sex, race, geographic location including urban location and the co-morbidity index. ICD-9 codes between the two practitioner groups were collected to control for the confounding factor of visit type. The window for imaging was also altered and statistical analyses were rerun to check for changes in statistical results.
Subsequently, the authors looked specifically at nonspecific lower back pain and acute respiratory infection as well as differences between NPs and PAs.
After inclusion and exclusion criteria were applied, 651,074 E+M visits (75.9% of all E+M visits) were eligible for analysis. 92% of the E+M visits were conducted by PCPs, whereas 8% of the visits were conducted by non-physician practitioners (NPPs). Most patients were female (59.5%) and healthy (89.7% with a CCI score of 0). Of all the qualifying visits, a single imaging event occurred in 1.9% of the visits, with the majority of these being radiography (72.2%), as opposed to advanced imaging methods.
Patients seen by PCPs were more likely to be older than 75, male, nonwhite, urban, and sicker.
The odds of an NPP ordering imaging for a patient in the office setting was 1.334 (1.267-1.424) compared to PCPs. This equates to 0.3% more images per episode of care. Similar odds ratios existed for the most frequently recorded ICD-9 conditions seen by PCPs. PCPs and NPPs ordered advanced imaging tests at the same rates in new patients, but NPPs had a higher rate of advanced imaging orders in established patients. In the subgroup analysis, NPs ordered 0.7% fewer imaging studies compared to PAs.
PPP Initial Discussion/Critique
According to the AHRQ, there are currently 209,000 primary care physicians. According to the AANP, there are approximately 270,000 nurse practitioners, of which 196,000 (72.6%) provide primary care. However, this study found that only 8% of E+M codes studies were coded for by NPPs. It is unclear if this was a good representation of NPP practices.
It is unclear why PCPs and NPPs had similar advanced imaging ordering practices for new patients but not for established patients. It is possible, as the authors suggest, that NPPs have more strict protocols for new patients. They may also be more likely to discuss these patients with their supervising physician or may not be doing as complete of a workup as is necessary, potentially missing the diagnosis.
A major limitation of this study is that the authors were unable to separate NPPs in supervised versus unsupervised states.
The authors concluded that “while increased use of imaging appears modest for individual patients, this increase may have ramifications on care and overall costs at the population level.” We agree, as 0.3% more images per episode of care is magnified greatly when you consider how many episodes of care exist in just one year for Medicare beneficiaries.
- The study found that 8% of visits were coded for by NPPs. However, AANP and AHRQ data suggests that there are a near equal number of PCPs and NPs practicing primary care. How can this be explained?
- Patients seen by physicians had lower imaging studies, although by a small margin. However, patients were older and sicker by co-morbidity index. Do you think this margin would be larger if PCPs saw similarly sick patients as NPPs?
- The study used Medicare beneficiaries who are were 66 or older. Is this study generalizable?
- While 0.3% more imaging studies by NPPs seems insignificant, it was 0.3% per episode of care. Does that change your thoughts? How?
- The authors report the subgroup analysis of NPs vs. PAs but don’t include data on number of PA visits. PAs have significantly less numbers than NPs overall. Does this have a potential effect on the validity of data?
- Why do you think NPPs had higher advanced imaging orders for established patients but not for new patients?
- Does this study support NPP independent practice?