Figure 2. Estimated Odds Ratios for 3 Successive Multilevel Regression Models.

Model 1 (orange boxes) includes elevated pretest risk of mutation carriage and the surgeon identifier as the only variables. Model 2 (blue boxes) adds the surgeon volume and the Tendency to Test Scale score that measured “tendency to order genetic testing.” Model 3 (black boxes) adds sociodemographic characteristics likely to reflect access to testing of patients. All models include a surgeon identifier and quantify the amount of residual variation attributable to the surgeon (surgeon variation in testing) that remains after the inclusion of the variables in each respective model. The odds ratio listed for the surgeon represents the amount by which a patient’s odds of having a genetic test are multiplied if she sees a surgeon with an observed propensity to test that is 1 SD above the average surgeon’s (in other words, a surgeon in the 84th percentile as opposed to the 50th percentile for propensity to test). Emory indicates Emory University (Atlanta, Georgia); USC, University of Southern California (Los Angeles); and VA, Veterans Affairs.