Comparison of Radiologists and Other Specialists in the Performance of Lumbar Puncture Procedures Over Time

DISCUSSION

In recent years, radiologists have become majority providers of lumbar punctures for Medicare Fee-for-Service beneficiaries, and the percentage of lumbar punctures performed by radiologists has increased in almost every practice setting and patient group. A dramatic shift in lumbar puncture procedures in the Medicare population to radiologists had been previously demonstrated using aggregate claims data, which reported that in 1991, only 10% of lumbar punctures were performed by radiologists, increasing to >45% by 2011.⁵ The present study uses a different and more detailed patient encounter-level Medicare dataset with procedural information through 2017 and confirms that this trend has continued. It additionally provides insight into discrepancies between specialty in factors such as place of service, day of week, and patient comorbidity.

Potential causes for the shift in lumbar punctures to radiology in Medicare beneficiaries can be conceptually subdivided into patient-level and provider-level factors. Patient-level factors include issues that impact the feasibility of lumbar puncture or increase the need for imaging guidance, including but not limited to patient habitus, scoliosis or spondylotic changes, and other medical comorbidities. Provider-level factors are issues that impact the ability or desire of medical practitioners to perform lumbar punctures themselves rather than refer the procedure to other providers. Provider-level factors include practice environment, which may or may not be conducive to bedside procedures, personal ability or confidence in performing lumbar punctures, and economic considerations.

In this study, the findings regarding lumbar punctures performed in the emergency department setting may provide insight into the relative importance of patient-specific and provider-specific factors in influencing what specialty group performs the procedure. In the emergency department, emergency medicine physicians performed most lumbar punctures, and this proportion remained steady during the study. However, there was minimal difference in the CCI between patients undergoing lumbar punctures by emergency medicine physicians and radiologists. While the CCI imperfectly captures patient-level factors that may make lumbar puncture technically challenging, the modest difference in comorbidity supports the hypothesis that lesser case complexity is not the primary factor behind the low proportion of lumbar punctures performed by radiology in the emergency department. Thus, the high percentage of emergency department lumbar punctures performed by emergency medicine physicians suggests that the procedure is technically feasible without fluoroscopic guidance in many patients, even within a typically older Medicare beneficiary population. The logical implication is thus that the shift of lumbar punctures to radiology from other specialties in the outpatient and hospital inpatient practice settings is likely due to provider-related factors rather than technical necessity.

If lumbar puncture practice is driven by provider-level factors, it is possible that the trend could reverse if those factors change. However, we believe that the chance of this happening decreases with time. For example, if extrinsic factors regularly interfere with nonradiology providers performing lumbar punctures, across time, those same providers may be less inclined to perform lumbar punctures due to limited recent experience. In surveys conducted by the American College of Physicians, 73% of internal medicine physician respondents in 1986 reported that performing lumbar punctures was part of their clinical practice, with a median of 5 lumbar punctures performed in the year preceding the survey; by 2004, only 26% of respondents performed lumbar punctures, and even this group reported a decrease in case numbers, to a median of 3 per year.¹⁹ In the present study, by 2017, just 2.6% of lumbar punctures in the Medicare population were performed by primary care specialties collectively, despite internists and family and general practitioners representing by far the largest physician specialty groups in the United States, illustrating the long-term consequences of these practice trends.²⁰

Ultimately, the determinant of whether specialties other than radiology and emergency medicine will continue to perform lumbar punctures in a meaningful capacity will be specialty training. If residents do not become facile with lumbar puncture during training, either because of expectations that the procedure should be performed by others or because their supervising faculty are themselves uncomfortable performing and teaching the procedure,^8,21 they are not likely to develop the skill thereafter. Neither neurology residency nor internal medicine residency training have a specific Accreditation Council for Graduate Medical Education–mandated number of lumbar punctures necessary for graduation, so it is likely that expectations vary greatly among programs. Furthermore, in internal medicine certification, the American Board of Internal Medicine no longer mandates demonstration of procedural skill for lumbar punctures, but simply, the cognitive competence of understanding procedural indications, technique, complication recognition and management, and other information needed to obtain informed consent.²² As might be expected, a recent publication found that 84% of lumbar punctures performed on internal medicine service inpatients at a single tertiary academic medical center were performed by radiology or a dedicated hospital procedural service rather than by the primary team.²³ To the authors' knowledge, no similar studies have been published evaluating the performance of lumbar punctures on inpatients by neurology services.

The potential for improvement in resident procedural training is well-recognized, and efforts are underway to improve trainee access to procedure opportunities.^24,25 In fact, some movement in this direction may already be occurring. In the hospital inpatient setting, the trend toward performance of lumbar punctures by radiology appears to have reached a plateau or even reversed slightly, with the proportion of lumbar punctures performed by radiology decreasing in 2016 and 2017. While future research will be needed to establish whether this reversal is a durable trend, it could plausibly be explained by some of the measures noted above.

Aside from radiologists, the only provider group that performed an increasing percentage of lumbar punctures across time was nonphysician providers. Although they performed only 7.5% of lumbar punctures in 2017, the most recent year of analysis, that was sufficient to make them the fourth most common provider group overall. Medicare claims by nonphysician providers are insufficient to determine their practice affiliations, and it is unclear what proportion are working within radiology groups to perform imaging-guided lumbar punctures versus performing bedside lumbar punctures in other settings. Increased collaboration between radiologists and nonphysician providers may represent a potential strategy for dealing with the demand for lumbar puncture.

Several potentially disadvantageous consequences of the shift in lumbar puncture performance to radiology merit discussion. From a patient care standpoint, it is often desirable to obtain CSF as expeditiously as possible, such as before or soon after the initiation of antibiotics for suspected bacterial meningitis or when ruling out subarachnoid hemorrhage. When one accounts for logistical considerations such as procedure scheduling, patient transportation, and fluoroscopy room preparation, even the most efficient radiology service is unlikely to rival the speed with which CSF can be collected at the bedside by an experienced provider. From a health system use-of-resources perspective, a lumbar puncture under fluoroscopic guidance requires the presence of both a radiologist and a radiologic technologist as well as use of a fluoroscopy suite, all increasing the per-procedure cost relative to bedside lumbar puncture. This cost is undoubtedly justified when lumbar puncture cannot be successfully performed without imaging, but may not be appropriate in all circumstances. Further-more, the diversion of radiologists from other tasks to lumbar punctures carries significant opportunity cost. As of 2020, performing a lumbar puncture with imaging guidance yields 1.73 work-relative value units, less than that for interpretation of an MR imaging of the brain with and without contrast, which yields 2.29 work-relative value units. Last, although the radiation dose to the patient and provider associated with a lumbar puncture is generally quite low, we must ask if even this minimal dose is justified by the corresponding benefits.²⁶

The primary limitations of this study are that it is restricted to the Medicare beneficiary population and that the administrative Medicare dataset does not contain all clinical variables that would be of interest. It is possible that the observed trend toward increased lumbar puncture performance by radiologists is less pronounced in younger adults, and particularly in children. In the pediatric population, lumbar punctures are often performed by pediatricians, though even in this group, the reported success rate of lumbar punctures is variable.^27,28 With regard to potentially relevant information not fully captured by the Medicare dataset, patient-level variables such as body mass index, the presence of scoliosis, and history of spine surgery would be indicators of lumbar puncture difficulty and would likely be superior to the CCI for this purpose. Additionally, aborted or incomplete lumbar punctures are likely under-reported, so the true rates of procedural success by specialty and the proportion of patients in whom lumbar puncture was attempted by other services before radiology referral cannot be determined. In light of these limitations, future studies in other patient populations will be necessary to fully understand practice patterns in lumbar puncture performance.