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Appendix A: General Scheme of a Cost Utility Analysis Economic Evaluation Steps 1. Ask a clear study question 2. Determine perspective to be used 3. Calculate direct costs associated with the two procedures 4. Review literature to identify all complications (health states) associated with these procedures and treatment of these procedures 5. Identify the probabilities and cost of each complication 6. Design a decision tree with branches showing health states and the probability of each 7. Measure utility and QALY for each complication pathway Example What is the more cost-effective procedure: the Deep Inferior Epigastric Perforator Flap (DIEP) or Free Transverse Rectus Abdominis Myocutaneous (TRAM) Flap for postmastectomy reconstruction? Third-party payer (Ministry of Health for Ontario) Direct medical costs taken from the third-payer perspective (surgical fees, anesthetist’s fees, hospital charges) from the Ontario Ministry of Health Schedule of Benefits For example, total/partial flap failure, hernia, abdominal wall weakness, fat necrosis, hematoma as well as the health state of “successful surgery”. For example the expected cost of for a hernia: 0.2 (probability of a complication occurring) x 0.04 (probability of a hernia occurring) x estimated cost ($1663.48) to give an expected cost = $13.31 (costs derived from the Ontario Ministry of Health Schedule of Benefits). Examples of two decision trees: To determine utilities of various health states associated with DIEP and free TRAM flaps, 32 plastic surgeons across Canada were asked to rank their preference using a ‘feeling thermometer’ (10 cm vertical ladder with 0 = death; 1 = perfect health). Successful surgery was determined to have a utility of 0.87. QALY was calculated using a hypothetical patient of 45 years with life expectancy of 78.6 years (statistic from Statistics Canada). QALY (complication) = [(duration of health state) x (utility of health state)] + [(# healthy years remaining – duration of health state) x (utility of successful breast reconstruction)] For example using hernia as the complication: = (0.31* x 0.66**) +((78.6 – 45 years) x 0.87) = 29.17 8. Calculate expected cost and expected QALY for each comparative intervention 9. Calculate ICUR and find if it falls within the acceptability threshold 10. Perform sensitivity analysis to see if the results are robust Please see Thoma & McKnight16 for more information. Utilities, Costs (CDN $), QALY of all Health States Use the equation: ICUR = (Mean CostDIEP – Mean CostTRAM)____ (Mean QALYDIEP – Mean QALYTRAM) Please see Thoma & McKnight16 for more information. Cost-utility Analysis: Baseline and Sensitivity Analyses Comparing Free TRAM and DIEP Flaps * 0.31 was determined by number of weeks/year = 16 weeks/52 weeks = 0.31 years ** 0.66 was the utility of health state determined from the vertical feeling thermometer from the 32 plastic surgeons Table adapted from: Thoma A, Veltri K, Khuthaila D, Rockwell G, Duku E. Comparison of the deep inferior epigastric perforator (DIEP) and free transverse rectus abdominis myocutaneous (TRAM) flap in post-mastectomy reconstruction: A cost-effectiveness analysis. Plast Reconstr Surg. 113: 1650, 2004