New research on the average number of surgical slices made during Mohs micrographic surgery (MMS) will serve as a first step towards identifying best practices for MMS, as well as identifying and informing physicians who may need re-training because their practice patterns deviate far from their peers.

The findings appear in JAMA Dermatology.

In an analysis of Medicare Part B claims data submitted by more than 2,300 United States physicians from January 2012 to December, the average number of cuts among all physicians was 1.74. The median was 1.69 and the range was 1.09 to 4.11 average cuts per case. Measuring a surgeon’s average number of cuts was recently endorsed by the American College of Mohs Surgery (ACMS) as a clinical quality metric used to assess its members.

The new analysis is part of a medical quality improvement project called “Improving Wisely,” funded by the Robert Wood Johnson Foundation and based at The Johns Hopkins University. The initiative focuses on developing and using individual physician-level measures to collect data and improve performance. The U.S. Centers for Medicare and Medicaid Services provided broad access to their records for the study.

To the Extremes: High and Low Outliers

Of the 2,305 physicians who performed MMS during each of the three years studied, 137 were considered extremely high outliers during at least one of those years.  (An extremely high outlier was defined as having a personal average of greater than two standard deviations, or 2.41 cuts per case, above all physicians in the study.) Forty-nine physicians were persistently high outliers during all three years.

Physicians in solo practice were 2.35 times more likely to be a persistent high outlier than those in a group practice; 4.5 percent of solo practitioners were persistent high outliers compared to 2.1 percent of high outlier physicians who performed MMS in a group practice, the study showed. Volume of cases per year, practice experience and geographic location were not associated with being a high outlier.

Low extreme outliers, defined as having an average per case in the bottom 2.5 percent of the group distribution, also were identified. Of all physicians in the study, 92 were low outliers in at least one year and 20 were persistently low during all three years.

Potential explanations for high outliers include financial incentive as  the current payment model for MMS pays physicians who do more cuts more money, the study authors note. These charges are ultimately passed on to Medicare Part B patients, who are expected to pay 20 percent of their health care bill. Low outliers may be explained by incorrect coding, overly aggressive initial cuts, or choice of tumors for which MMS is not necessary, they write.

The researchers also gathered the following data for each physician: sex, years in practice, whether the physician worked in a solo or group practice, whether the physician was a member of ACMS, whether the physician practiced at an Accreditation Council for Graduate Medical Education site for MMS, volume of MMS operations, and whether the physician practiced in an urban or rural setting. Physicians had to perform at least 10 MMS procedures each year to be included in the analysis.

Although the study was limited by lack of information about each patient’s medical history, or the diameter or depth of each cut, it’s a meaningful step toward identifying and mitigating physician outliers, the study authors conclude.

Funding for this study was provided by a grant from the Robert Wood Johnson Foundation and the ACMS.