Given increases in health care spending in the United States and worldwide, it goes without saying that policy makers and payers are interested in finding ways to reduce costs without compromising quality of care. One effort that is receiving attention is whether mid-level providers, such as physician assistants, nurse practitioners, and nurse anesthetists, should play a greater role in care delivery.1,2 This question is particularly salient in the case of anesthesiology, where the degree to which nurse anesthetists should be supervised by physicians (typically an anesthesiologist, although occasionally the proceduralist) remains an area of active debate3 with important policy implications. For example, state-level efforts to “opt out” of federal regulations requiring anesthesiologist supervision of nurse anesthetists remain a continued area of contention and an object of great concern for both the American Society of Anesthesiologists and the American Association of Nurse Anesthetists. Therefore, characterizing the degree and extent to which nurse anesthetists require supervision by an anesthesiologist is a question with important policy implications.
However, answering this question well is difficult. First, as demonstrated by others,4,5 “supervision” is a term describing a continuum of interactions between the anesthesiologist and the nurse anesthetist. On one extreme would be true independent practice (where the anesthesiologist neither sees the patient nor coordinates care with the nurse anesthetist), whereas the other extreme would involve near-total involvement by the anesthesiologist, for example, the supervision accorded to new anesthesia trainees (i.e., new anesthesia residents or registrars). Therefore, it may be difficult to precisely measure what degree of supervision was provided on a given case. Second, “bad” outcomes in anesthesia are thankfully rare, which means that studies limited to a single institution, or even a group of institutions, may not have the power to determine clinically or statistically significant differences in outcomes.
Administrative claims data, such as data from the United States Centers for Medicare and Medicaid Services (CMS), would seem to provide one way around this issue. These data sets have the advantage of being large, containing data for millions if not tens of millions of patients, allowing for statistical precision. Moreover, in the United States, the health care claim submitted by the anesthesia provider indicates whether a nurse anesthetist provided care, as well as a code, the modifier “QZ,” which indicates that the nurse anesthetist provided care without medical direction by an anesthesiologist. Indeed, a recent, widely publicized study using data from the CMS found no differences in outcomes when care was administered by nurse anesthetists billing under the modifier QZ, leading to the conclusion that independent nurse anesthetist practice is not associated with worse outcomes.3
But does the modifier QZ truly identify independent practice? By definition, it indicates the absence of medical direction, but this may not be the same as independent practice or the absence of supervision by an anesthesiologist. Medical direction is a formal term defined and used by the CMS (and private insurers) for provider payment purposes. It requires the anesthesiologist to perform and document his or her presence in 7 activities, such as participating in the key portions of the case and being physically present and available for emergencies.a Although the presence of the anesthesiologist implies that the nurse anesthetist did not practice independently, the converse may not hold. For example, if an anesthesiologist was present for all 7 activities but did not document his or her presence, the anesthesiologist could not bill for medical direction, and therefore, the case would be billed under the modifier QZ, despite the presence of the anesthesiologist in the case. This possibility is particularly salient, because in the United States, the presence or absence of the modifier QZ does not change the amount of money paid to the anesthesia group for a given case.b However, as noted earlier, the presence of an anesthesiologist reduces the amount of required documentation. Accordingly, there is a potential incentive for groups to bill the modifier QZ even if an anesthesiologist supervises (and even meets the requirements for medical direction) for a given case.
In a recent study, Miller et al.6 explored this issue by examining whether institutions where every anesthesia claim includes the modifier QZ also have affiliated anesthesiologists. The underlying logic is simple: If the modifier QZ truly represents independent nurse anesthetist practice, then why would these facilities have affiliated anesthesiologists? They find that anesthesiologists are in fact affiliated with a large percentage of these institutions, thereby casting doubt on whether the modifier QZ does indeed represent independent practice, particularly at larger institutions (institutions reporting ≥70 cases), where the authors find the median number of anesthesiologists per facility to be 5.33 and the median ratio of nurse anesthetists to anesthesiologists to be 3.47:1. Thus, even though these institutions may report every anesthetic as being performed without medical direction, it seems clear, based on the number of affiliated anesthesiologists and the ratio of nurse anesthetists to anesthesiologists, that anesthesiologists are playing an important role in the anesthetics performed at the given institution. However, things are less clear for smaller institutions, where the authors typically find 0.5 anesthesiologists per hospital and the ratio of a nurse anesthetist to anesthesiologist ratio ranging from 2.00 to 14.62. With so few anesthesiologists at these institutions, it certainly may be the case that a large fraction of the anesthetics are provided by nurse anesthetists practicing independently.
As the authors note, one of the direct implications of their results is that we should view with caution any study using the modifier QZ to identify independent nurse anesthetist practice. Although administrative claims data may be useful given their large size, currently, the modifier QZ does not reliably identify independent nurse anesthetist practice, particularly at larger institutions. This is a serious limitation to several studies3,7 that have used the modifier QZ to assess whether independent nurse anesthetist practice is associated with worse outcomes.
The findings of the authors also have an important policy implication: they suggest that the definition of the modifier QZ should be changed to better reflect the actual roles of the anesthesiologist and the nurse anesthetist for 2 reasons. First, characterizing the optimal level of supervision for nurse anesthetists could improve the efficiency of the health care system and is therefore an important policy question. Therefore, changing the definition of the modifier QZ, such as making it a more continuous variable to better reflect the degree of supervision by the anesthesiologist, could improve policy making. Second, increasingly, payers are using claims data to measure quality and adjust payments accordingly (e.g., the Physician Quality Reporting System in the United States). Therefore, it is important to have billing codes that accurately reflect the nature and type of care that was actually provided to the patient.
As the old computer science saying goes, “Garbage in, Garbage out.” It seems clear that the modifier QZ has some serious limitations in identifying independent nurse anesthetist practice. In the short term, this casts some doubts on studies that have used code to identify whether nurse anesthetists are practicing independently. In the longer term, we should devise billing codes that more accurately reflect the roles of individuals in the anesthesia team to provide useful information to policy makers, payers, and researchers.
a See https://www.cms.gov/Regulations-and-Guidance/Guidance/Transmittals/downloads/R1859CP.pdf. Accessed September 22, 2015.
b With the “QZ” code, the nurse anesthetist receives 100% of the payment for the given case, whereas, with medical direction, the nurse anesthetist and the anesthesiologist each receive 50% of the payment. Regardless, the total payment (which would accrue to the group employing the anesthesiologist and the nurse anesthetist) remains the same.
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