Table 1.
Comparison of Baseline Characteristics Between the Historical and Intervention Cohorts
| Characteristic | Full unadjusted cohorts
|
Propensity-matched cohorts
|
||||
|---|---|---|---|---|---|---|
| Historical (N=184) |
Intervention (N=89) |
Standardized difference* | Historical (N=80) |
Intervention (N=80) |
Standardized difference* | |
| Age at surgery (years), Mean (SD) | 62.4 (12.4) | 64.0 (11.6) | 0.132 | 64.0 (13.1) | 64.4 (12.0) | 0.030 |
| BMI (kg/m2), Mean (SD) | 28.7 (7.7) | 29.2 (7.9) | 0.064 | 28.8 (8.4) | 29.6 (7.8) | 0.098 |
| Elixhauser comorbidity count, Mean (SD) | 2.3 (1.7) | 2.2 (1.7) | 0.030 | 2.2 (1.8) | 2.4 (1.6) | 0.11 |
| Current tobacco use | 13 (7.1%) | 12 (13.5%) | 0.213 | 9 (11.3%) | 7 (8.8%) | 0.083 |
| Diagnosis | ||||||
| Ovarian cancer | 152 (82.6%) | 74 (83.1%) | 0.014 | 64 (80.0%) | 66 (82.5%) | 0.064 |
| Endometrial cancer | 32 (17.4%) | 15 (16.9%) | 16 (20.0%) | 14 (17.5%) | ||
| Stage | ||||||
| I–II | 31 (16.8%) | 15 (16.9%) | 0.000 | 15 (18.8%) | 14 (17.5%) | 0.032 |
| III–IV | 107 (58.2%) | 46 (51.7%) | 0.130 | 40 (50.0%) | 40 (50.0%) | 0.000 |
| Recurrent | 46 (25.0%) | 28 (31.5%) | 0.144 | 25 (31.3%) | 26 (32.5%) | 0.027 |
| Residency† | ||||||
| Local | 24 (13.2%) | 13 (15.3%) | 0.060 | 10 (12.5%) | 12 (15.0%) | 0.070 |
| Regional | 70 (38.5%) | 35 (41.2%) | 0.060 | 37 (46.3%) | 33 (41.3%) | 0.100 |
| National | 84 (70.6%) | 35 (41.2%) | 0.100 | 31 (38.8%) | 33 (41.3%) | 0.050 |
| International | 4 (2.2%) | 2 (2.4%) | 0.010 | 2 (2.5%) | 2 (2.5%) | 0.000 |
| Insurance status† | ||||||
| Government | 87 (47.8%) | 43 (50.6%) | 0.060 | 45 (56.3%) | 43 (53.8%) | 0.050 |
| Private | 94 (51.7%) | 41 (48.2%) | 0.070 | 34 (42.5%) | 36 (45.0%) | 0.050 |
| Self-pay | 1 (0.6%) | 1 (1.2%) | 0.070 | 1 (1.3%) | 1 (1.3%) | 0.000 |
Abbreviations: ASA, American Society of Anesthesiologists; BMI, body mass index; IQR, interquartile range; SD, standard deviation; VTE, venous thromboembolism.
Covariate imbalance between the historical and intervention groups was assessed by evaluating the standardized difference for each baseline covariate, separately in the full unadjusted cohorts and in the propensity-matched cohorts. The standardized difference for a continuous covariate is defined as the absolute difference in surgical group means divided by an estimate of the pooled standard deviation. The derivation is similar for nominal covariates. A standardized difference less than 0.10 is considered by some authors to denote negligible covariate imbalance between groups.
Data available on 182/184 in the historical cohort and 85/89 in the intervention cohort.