In the classical conception of medicine as a profession, medical practice is supposed to be uniform because of the shared body of (theoretical) knowledge. Variation originates from the necessity to apply this theoretical knowledge to individual patients. The underlying assumption is one of professional autonomy; the decision of physicians is influenced by science and the medical condition of the patient only.
Residual variation still remains, however, when clinical variables and patient characteristics are taken into account and this residual variation is not random, but shows clear patterns. The most studied ones are small area variations (Wennberg and Gittelsohn 1975
; Ashton et al. 1999
). Researchers differ as to the attribution of this residual variation, some arguing that physicians prefer different practice styles, e.g., as a result of their education and professional socialization. The spatial phenomenon then emerges as a result of (self-)selection of physicians in certain areas or adaptation of preferences to those of others, resulting in a typical “surgical signature.”
Other researchers have argued that the circumstances under which physicians work have a profound influence on their decisions, and that these shared circumstances make for homogeneity and differing circumstances result in variation. Freidson (1975)
argued that in group practice, physicians cannot make their decisions autonomously, because they depend on colleagues, and are controlled by them. Although individual physicians can be conscientious and ethical, circumstances can cause them to change their performance.
The physician influence on utilization of care has been the subject of several studies (e.g., Burns and Wholey 1991
; Geller, Burns, and Brailer 1996
). In a study by Burns, Chilingerian, and Wholey (1994)
it was concluded that the physician is an important source of variation. Freidson (1975)
stated that the social environment in which physicians work is more important for their medical behavior than their formal professional education. For instance physicians working in hospitals are subject to collegial norms, affecting their (medical) behavior. Coser (1957)
demonstrated that there are different norms between wards within the same hospital. These differences, informal as opposed to formal, were related to different constraints because of differences in medical tasks. The wards, surgical and medical, were situated on two sides of the same floor.
In the debate in which explanations for variation are sought, the question arises at what level of analysis homogeneity might be expected. Reasoning from shared circumstances as a source of homogeneity, this study focused on hospitals as more appropriate than areas (unless areas are defined on such a scale that they form the market area of a single hospital). Because we studied several DRGs separately, this is equivalent to studying wards of the same specialty. The hypothesis that variation within hospitals was small compared with variation between hospitals was confirmed in this study and persistent over 3 years, in most of the study populations.
This result, however, is still compatible with both the approach based on preferences for a certain practice style and the approach based on work circumstances. We therefore also analyzed the decisions of the same physicians in different hospitals. Preferences for a certain practice style are supposed to be relatively stable within the same person, but circumstances may clearly differ. Different analyses confirmed that physicians working in two hospitals with different average lengths of stay have a length of stay similar to the usual practice in the hospital where the procedure was performed.
Underlying assumption in our study is that the physician, not the hospital, decides over patients' discharges. The hospital–physician relationship has changed from physician owned in the early twentieth century to one of joint control in the late 1980s (Shortell 1991
). However, the lack of common economic incentives makes it difficult for physicians and hospitals to cooperate (Shortell et al. 2000
). With a change from professional dominance to managerial-market orientation (Scott et al. 2000
), the question of whether the within-hospital similarities are choice or constraint is raised. Are physicians the central actors, or is it management? It might be that in the modern hospital formal management is more important than normative control by physicians. Still, it is the physician who signs the discharge note, and who runs the risk of malpractice suits. For the hospital, although there are incentives to do less, quality is important as well. Therefore, although regulative control might have become more important, physicians can still be considered important actors in the length of stay decisions. The physician is the one who discharges patients, and patients can only be discharged on the day their physician is around.
However, this might change in the future when for instance hospitalists, physicians used by the hospital, sign discharge notes for patients of other physicians. For hospitals this has the advantage of being able to discharge a patient, who is in the condition of being discharged, when the physician is not around.
The hypothesis that variation within a hospital would be smaller when more physicians practice in that hospital alone was not confirmed. This finding could be, however, because of the fact that there are not many hospitals in which there is a low proportion (range 0.16–0.99, mean 0.82) of physicians working only in that hospital. Results in this study are consistent with the results found in the study by Westert, Nieboer, and Groenewegen (1993)
and the study by Griffiths, Waters, and Acheson (1979)
This study demonstrated that hospitals are important in studying variation in physicians' practice and explaining length of stay and practice variation. It is important to understand the variation phenomenon, because it will facilitate effective interventions to improve quality of care (Blumenthal 1994
). Knowing where variation originates, combined with knowledge about which variation is undesirable, is the key to successful interventions. The existence of variation is often interpreted as a sign of overuse of health care resources and resources could be saved if all physicians adapted to the lowest utilization rates (Fisher et al. 1994
). Although overuse gets more attention, however, underuse could be a problem as well (McNeil 2001
). Sources of undesirable variation need to be identified, whether they are indicators of overuse or underuse, with an emphasis on those sources that can be influenced to improve the quality of medical care. If similar patients receive different treatments, or if in some areas it is more likely to receive a certain procedure than in others, some do not get what they need, or get more than they need. Both are undesirable. The former meaning that some people's health could be improved, the latter that there is a waste of resources by providing ineffective, unnecessary care. Part of variation can be legitimate, while another part is not. That part of variation that is not legitimate should be reduced. Although, up to now, there is no evidence that less variation is related to a higher quality of care (Weide et al. 1999; Fertig et al. 1993
). Patients should receive the treatment that works best, against acceptable costs. So, besides the question whether variations matter for mortality, morbidity, and quality of life, the question whether some patients receive high quality of care against lower costs is important.
Beyond the importance of understanding the variation phenomenon, it is necessary to study physicians who practice in more than one hospital. Previous research showed that length of stay was longer for the medical patients and shorter for the surgical patients of physicians working in several hospitals, and it was found that inpatient resource use is higher for physicians working in several hospitals (Burns and Wholey 1991
; Burns, Geller, and Wholey 1995
; Miller, Welch, and Welch 1996
In this study, we did not find that physicians who practice in two hospitals choose different lengths of stay compared with physicians who practice in one hospital only. We found instead, that multihospital physicians had lengths of stay comparable with the usual practice in the hospital. This implies that physicians adjust to colleagues or circumstances in the hospital where they perform procedures. This implication is useful in our understanding of the variation phenomenon; there are forces within shared work environments that cause physicians to make similar decisions. In this study, we were not able to distinguish between influences exerted by colleagues and by circumstances. This could have been performed if specific characteristics of the hospital had been taken into account. Those characteristics were unknown.
Patient selection could also be an explanation. Multihospital physicians may apply some criterion that is possibly related to length of stay, when choosing the hospital to which they admit patients. This, however, would reinforce the theory of the influence of the hospital on length of stay. The purpose of this article is not to describe differences between hospitals based on patient selection and therefore the possibility of composition effects should be excluded as much as possible. We did this by adjusting for case mix including severity of illness.
An important question is whether these work environments can be used in interventions to improve the quality of medical care. Several further possible explanations remain for the patterns of variation within work environments. It may be that physicians adapt to the colleagues they work with—that they follow the pack as Eddy (1984)
called it—or that there is another factor in the work environment, such as hospital management or the availability of beds and facilities (Westert 1992
; Westert and Groenewegen 1999
; Kroneman 2001
), which influences their medical choices.
There is probably not one single explanation, although one might be more important than the other. If variation is very much related to the influence of colleagues, consensus conferences are a useful instrument for effective interventions. Two strategies could be applied, via broad conferences trying to influence physicians from many different hospitals to adopt the same evidence-based standards and guidelines, or hospital-based conferences trying to influence all physicians in a certain group to change their “local standards” toward more global, evidence-based standards. It is, however, questionable whether conferences are effective in changing physician behavior, or that stronger interventions should be developed. Thom (2000)
showed in a study on the effects of a training course for physicians to improve their behavior and to increase patients' trust, that the intervention was not strong enough. Available evidence suggests that physician profiling can be efficient (Evans, Hwang, and Nagarajan 1995
). Physician profiling is a technique used to change hospital length of stay choice of physicians, by comparing their individual average to a benchmark figure, adjusted for severity of illness. The physicians are confronted with their average, without knowing the average of their direct colleagues. This individual-based, managerial approach avoids the informal standards within a hospital, which could be a barrier when trying to influence length of stay choices in a group approach. Managerial interventions might be more effective when applied to individuals, while interventions focusing on professional content might be more effective when the approach is based on teams of physicians.