Table 2. Results From Multivariable Difference-in-Differences Analyses Comparing Patients Undergoing SG vs RYGB Between 2008 and 2016 Across Categories of Ambulatory Care Costs and Usea.
| Cost category | Postoperative year 1, SG (n = 3049) vs RYGB (n = 3251) | Postoperative year 2, SG (n = 1952) vs RYGB (n = 2173) | Postoperative year 3, SG (n = 1054) vs RYGB (n = 1151) | Postoperative year 4, SG (n = 514) vs RYGB (n = 643) | ||||
|---|---|---|---|---|---|---|---|---|
| Absolute difference (95% CI), $b | Relative difference, % (95% CI)c | Absolute difference (95% CI), $b | Relative difference, % (95% CI)c | Absolute difference (95% CI), $b | Relative difference, % (95% CI)c | Absolute difference (95% CI), $b | Relative difference, % (95% CI)c | |
| Total ambulatory care costs | −421.9 (−1334.1 to 490.4) | −5.3 (−16.1 to 5.6) | −642.9 (−1643.4 to 357.5) | −8.4 (−20.5 to 3.7) | −138.9 (−1273.2 to 995.4) | −2.0 (−17.8 to 13.9) | 382.8 (−1366.0 to 2131.6) | 5.1 (−19.2 to 29.5) |
| Prescription drug costs | 36.1 (−252.0 to 324.3) | 1.7 (−11.9 to 15.2) | 173.3 (−80.1 to 426.7) | 9.7 (−5.6 to 25.1) | 140.2 (−283.0 to 563.3) | 7.1 (−15.6 to 29.9) | 852.8 (395.6 to 1310.0)d | 52.4 (17.8 to 87.0)e |
| Office visit costs | −36.7 (−103.5 to 30.1) | −4.1 (−11.2 to 3.1) | −14.4 (−85.4 to 56.5) | −1.7 (−10.1 to 6.6) | −2.0 (−87.1 to 83.1) | −0.3 (−11.1 to 10.6) | −43.8 (−176.1 to 88.5) | −5.3 (−20.5 to 10.0) |
| Laboratory costs | −118.9 (−220.2 to −17.5)f | −13.9 (−24.2 to −3.6)e | −107.6 (−197.2 to −18.1)f | −15.9 (−27.4 to −4.5)e | −106.7 (−244.5 to 31.1) | −18.0 (−37.5 to 1.4) | −4.0 (−116.7 to 108.7) | −0.8 (−23.6 to 22.0) |
| Radiology costs | −4.6 (−97.7 to 88.5) | −0.7 (−15.5 to 14.1) | −63.6 (−189.7 to 62.6) | −9.2 (−26.0 to 7.6) | 6.7 (−121.7 to 135.0) | 1.1 (−20.3 to 22.5) | 22.5 (−150.8 to 195.7) | 3.4 (−23.7 to 30.6) |
| All other outpatient costs | −264.7 (−945.4 to 416.1) | −7.7 (−26.1 to 10.7) | −600.9 (−1432.8 to 231.0) | −16.4 (−35.7 to 3.0) | −164.6 (−1103.8 to 774.6) | −5.1 (−33.2 to 22.9) | −537.1 (−1900.9 to 826.7) | −13.9 (−45.1 to 17.2) |
Abbreviations: RYGB, Roux-en-Y gastric bypass; SG, sleeve gastrectomy.
Difference-in-differences analyses adjusting for all matched variables were used to generate between-group estimates for change in each outcome, at each time period, relative to a preoperative baseline period spanning months −24 to −13 before the index surgical date. Year −2 was selected as the preoperative baseline for comparison because the year immediately before surgery represents a very high utilization time, owing to preoperative workup.
Absolute differences in each period refer to the estimated actual change in costs among patients undergoing SG minus those among patients undergoing RYGB in that segment vs baseline (months −24 to −13), accounting for all other periods.
Relative differences in each period refer to the estimated relative difference between SG and RYGB groups vs baseline, accounting for all other periods.
P < .001.
P < .01.
P < .05.