LAUSR

the proportion of missing data for 5 of the 11 comorbidity variables included within the mFI increased over time. Specifically, the variables “history of myocardial infarction,” “history of percutaneous intervention, coronary stenting or cardiac surgery,” “history of peripheral vascular disease, rest pain or gangrene,” “history of impaired sensorium,” and “history of transient ischemic attack” were missing for 100% of patients in 2013 compared with 54.9% of patients in 2011. Furthermore, the missing data were not missing at random. Although an increasing mFI score was associated with greater odds for postoperative mortality, the mFI demonstrated poor discrimination for the years between 2005 and 2013 (area under the curve: range, 0.56-0.65) (Table 2). To assess the extent of missing data within the data set, additional analyses were performed among patients undergoing an esophagectomy (Current Procedure Terminology code 43107, 43112, 43117, 43121, and 43122) or a total hip replacement (Current Procedure Terminology code 27130). Of note, a similar pattern of missing data was also observed among these patients. Of the variables “history of myocardial infarction,” “history of percutaneous intervention, coronary stenting or cardiac surgery,” “history of peripheral vascular disease, rest pain or gangrene,” “history of impaired sensorium,” and “history of transient ischemic attack,” 43.7% and 66.5% of data were missing for esophagectomyandtotalhipreplacement,respectively, in2011,whereas 100% of data was missing in 2013 for both esophagectomy and total hip replacement (data not shown).