Addressing unwarranted variation: literature review on methods for influencing practice

Addressing unwarranted variation: literature revie…
01 Mar 2014

Variation in medical practice has become a major topic of inquiry for health services researchers. Investigators have frequently documented variation in the way in which health services are delivered, both among individual clinicians and across geographic areas, and have found that such variation often cannot be explained by demographic factors or other determinants of health need. The existence of such unexplained variation has provoked questions about the effectiveness, efficiency and quality of health care services.

Observations of variation have consequently been used to justify a variety of policies aimed at reducing variability, such as greater emphasis upon outcomes research, feedback to practitioners, and closely monitored performance measures.

Not all variation is undesirable, however. The trick is in reducing the bad variation, which reflects the limits of professional knowledge and failures in its application, while preserving the good variation that makes care patient centred. (Mulley 2010)

John Wennberg, who has championed research into clinical variation in the United States (US) over four decades (including founding the innovative Dartmouth Atlas of Health Care (2014)) defines unwarranted variation in health care as variation that cannot be explained on the basis of illness, medical evidence or patient preference (Wennberg 2010). Wennberg (2011) groups clinical care into three categories for understanding variation:

  1. Effective care is defined as interventions for which the benefits far outweigh the risks; in this case the ‘right’ rate of treatment is almost every patient defined by evidence-based guidelines to be in need. Unwarranted variation is generally a matter of underuse.
  2. Preference-sensitive care is when more than one generally accepted treatment option is available, such as elective surgery. The right rate should depend on informed patient choice, but treatment rates can vary extensively because of differences in professional opinion.
  3. Supply-sensitive care comprises clinical activities such as doctor visits, diagnostic tests and hospital admissions, for which the frequency of use relates to the capacity of the local health care system. The key issue with this one is that, at least in the US, those living in regions with a high-intensity pattern of care have worse or no better survival than those living in low-intensity regions. This means that greater intensity of care does not necessarily equate to improved outcomes.

Collating and presenting evidence of health care variations is a key first step. Knowledge does not, unfortunately, always lead to action. The purpose of this literature review, therefore, is to set out approaches that have been and are being used overseas to identify and manage unwarranted variation.

Page last modified: 15 Mar 2018