Appendectomy

The Clinformatics™ Data Mart captures administrative health claims across the United States for members of a large national managed care company affiliated with OptumInsight (Eden Prairie, MN). We examined claims from January 1, 2012 to June 30, 2015 among adults ages 18 to 64 to capture surgical procedures performed between 2013 and 2014 to account for the 12-month preoperative and 6-month postoperative study period. We included only individuals with continuous medical and prescription drug coverage to evaluate the complete health care experience. We excluded patients ages 18 and younger, as well as patients older than 64 years due to incomplete capture of Medicare Part D prescriptions claims data. The study was deemed exempt from review by the University of Michigan Institutional Review Board.
We selected 13 common elective surgical procedures, and categorized these into minor and major groups based on prior literature. Minor surgical procedures included varicose vein removal, laparoscopic cholecystectomy, laparoscopic appendectomy, hemorrhoidectomy, thyroidectomy, transurethral prostate surgeries, and parathyroidectomy. Major surgical procedures included ventral incisional hernia repair, colectomy, reflux surgery, bariatric surgery, and hysterectomy. We identified patients undergoing surgery using Current Procedural Terminology (CPT) or International Statistical Classification of Diseases and Related Health Problems (ICD9_ procedure codes (Supplemental Table 1).
We sought to determine new persistent opioid use after surgery, and included only patients who filled an opioid prescription fill either in the month prior to surgery or within two weeks after discharge. Comparable to previous studies of opioid naïve surgical populations,^{7 (link),8} patients who had filled one or more prescriptions for opioids 12 months to 31 days prior to their surgical procedure were excluded from the analysis (Figure 1). To account for prescriptions provided preoperatively for postoperative pain control, patients filling opioids in the 30 days prior to surgery were included, and prescriptions filled in this time was included as a covariate in the analyses. Lastly, we excluded patients who underwent additional surgical procedures during the study period using subsequent procedural codes for anesthesia in the 6-month postoperative period.
As a comparison cohort of patients who did not undergo surgery, we identified a random 10% sample patients ages 18 to 64 years of age who did not undergo surgery in the study period We included only patients in the nonoperative group who did not fill an opioid prescription during a 12 month period and did not have any codes for surgical procedures or anesthesia during this period. These patients were then given a random date of surgery. No patients had an opioid fill in the year prior to their fictitious surgery date nor did they have any anesthesia codes in the 6 months following their fictitious surgery date.

We constructed a sample consisting of patients who underwent 1 of 11 surgical procedures during the sample period: total knee arthroplasty (TKA), total hip arthroplasty (THA), laparoscopic cholecystectomy, open cholecystectomy, laparoscopic appendectomy, open appendectomy, cesarean delivery, FESS, cataract surgery, transurethral prostate resection (TURP), or simple mastectomy. We chose these procedures because they are commonly performed. In addition, with the exception of TKA and THA, these procedures are not indicated to relieve pain and are not thought to place patients at risk for long-term pain. We identified patients who underwent these procedures by identifying inpatient or outpatient claims with a CPT code for the given procedure (eTable 1 in the Supplement). We restricted our analysis to patients aged 18 to 64 years who were continuously enrolled for a period of at least 3 calendar years, encompassing the year before the procedure and the year after. For example, for patients who received their procedure in 2003, we required that the patient be continuously enrolled for at least the time period January 1, 2002, through December 31, 2004. In addition, we excluded patients who underwent 2 or more of the 11 studied surgical procedures. Using data from pharmacy claims, we further restricted our analysis to opioid-naive patients, defined as patients who did not fill a prescription for an opioid in the 12 months prior to their procedure. A flowchart outlining the construction of the sample is provided in the eFigure in the Supplement.