Appendix

Table A1 Parameter estimates of the transition probabilities in the Markov model

Transition probability / Estimatesa / Rangeb / Distribution / Sources
Age-dependent annual mortality risk for women in general population / Life-table of annual mortality risk among women in Ontario in 2007 / N/A / 24
Risk of having ectopic pregnancy for women after conducting THC or Tubal Coagulation procedures / For THC, 10-year risk of having ectopic pregnancy is 1 per 1000 procedures
For TC, 10-year risk of having ectopic pregnancy is 4 per 1000 procedures / Beta / 25
Risk of having ovarian cancer for women of all ages / Lifetime risk of having ovarian cancer is about 1.5% among general population in Canada / Beta / 2
Mortality risk of having ectopic pregnancy when having surgical procedure / 1 in 100 000
Percentage of reduction of lifetime risk of having ovarian cancer after having bilateral salpingectomy surgical procedure / 50% reduction of risk in having ovarian cancer / (20%–80%) / Beta / 21
Percentage of reduction of lifetime risk of having ovarian cancer after having ectopic pregnancy / 25% reduction of risk in having ovarian cancer / (10%–40%) / Beta / Assumption
Risk of having recurrent of ovarian cancer, stage I–IV / Stage I/II: < 5% / (0%–5%) / Beta / Assumption
Stage III/IV: 20% / (10%–20%)
5-year survival rate for women who have ovarian cancer, stage I–IV / Stage I: 92.6% / Beta / 26
Stage II: 70.5%
Stage III/IV: 20% / (15%–25%)
5-year survival rate for women who have recurrent ovarian cancer (assumed stage III/IV) / Stage I–IV, 5-year survival rate of having recurrent ovarian cancer is about 20% / (15%–25%) / Beta / 26

TC: tubal coagulation; THC: tubal Hulka clip.

A majority of data sources were obtained from Canadian literature to reflect the characteristics of Canadian population and the condition of the Canadian health care system.

aAll the risks have been converted to an annual risk in the Markov model.

bRange is used for probabilistic Markov model.

Table A2 Health state utilities measured as QALYs

Health state / Duration / Utilities (QALYs) / Source
Perfect health / 1 year / 1.0
Newly serous ovarian cancer, stage I/II / 1 year / 0.81 (0.03–0.97) / 20–22
Newly serous ovarian cancer, stage III/IV / 1 year / 0.55 (0.03–0.93) / 20–22
Recurrent of ovarian cancer, stage I/II / 1 year / 0.47 (0.03–0.93) / 20–22
Recurrent of ovarian cancer, stage III/IV / 1 year / 0.40 (0.03–0.93) / 20–22
Newly-diagnosed ovarian cancer, stage III/IV / 24 weeks / 0.50 (0.03–0.93) / 20–22
Recurrent ovarian cancer, stage III/IV / 24 weeks / 0.50 (0.03–0.93) / 20–22
Recurrent ovarian cancer, stage III/IV / 24 weeks / 0.42 (0.03–0.93) / 20–22
Ectopic pregnancy / 4 weeks / 0.58 / 23
Recovery from ectopic pregnancy / 1 year / 0.9 / a
Death / 1 year / 0.0

aWe assumed that women after having ectopic pregnancy procedure may reduce their health state by 10% of the prefect health state.

Table A3 Lifetime costs (2016 present values) for each sterilization procedure conducted at Toronto East Teaching Hospital in the year of 2016

Cost component / Surgical procedures
Laparoscopic bilateral salpingectomies / Laparoscopic hulk clips / Laparoscopic tubal coagulation
Treatment (includes first-line and recurrent chemotherapy) / $192 (95% CI $79–$338) / $382 (95% CI $257–$543) / $380 (95% CI 256–$542)
Surgical procedure / $1876 / $1498 / $1338
Ectopic pregnancy / $0 / $6 (95% CI $3–$10) / $24 (95% CI $12–$41)
Loss of wages for patients / $13 550 (95% CI $12 978–$14 214) / $14 584 (95% CI–$14 263, $14 931) / $14 576 (95% CI $14 257–$14 921)
Loss of wages for caregivers / $55 (95% CI $16–$115) / $110 (95% CI $37–$200) / $110 (95% CI $37–$200)
Total costs (from a societal perspective) / $15 673 (95% CI $14 979–$16 488) / $16 580 (95% CI $16 084–$16 824) / $16 428 (95% CI $14 905–$16 247)

Table A4 Sensitivity analysis (for assuming that women who make a decision for sterilization at age 40 years)

Strategy / Incremental saving / Incremental life gains / Incremental incident ovarian cancer cases / Incremental QALYs / ICER per life-year gain / ICER per QALY / ICER per case
Mean (SD) / Mean (SD) / Mean (SD) / Mean (SD) / Estimate (95% CI) / Estimate (95% CI) / Estimate (95% CI)
Age at 35 years
Laparoscopic bilateral salpingectomies vs. laparoscopic tubal clips / $1132 (490) / 0.14 (0.05) / 75 (24) / 0.05 (0.02) / $7684 ($4163–$9538) / $19 700 ($9347–$25 211) / $14 ($8–$18)
Laparoscopic bilateral salpingectomies vs. laparoscopic tubal coagulation / $980 (490) / 0.14 (0.05) / 74 (24) / 0.07 (0.02) / $6535 ($1378–$8886) / $13 920 ($1999–$20 672) / $12 ($3–$17)
Age at 45 years
Laparoscopic bilateral salpingectomies vs. laparoscopic tubal clips / $674 (344) / 0.08 (0.03) / 59 (19) / 0.04 (0.01) / $7567 ($1417–$10 675) / $15 580 ($2586–$22 514) / $11 ($2–$15)
Laparoscopic bilateral salpingectomies vs. laparoscopic tubal coagulation / $523 (344) / 0.08 (0.03) / 58 (19) / 0.05 (0.01) / $5517 (−$3572 to $9515) / $9665 (−$4045 to $17 350) / $8 (−$5 to $13)