Table 1.
Baseline characteristics and thrombosis during follow-up in 1:2 propensity-score-matched patients with Polycythemia Vera treated with phlebotomy only or hydroxyurea
| 1:2 random-samplea matched cohort (n = 951) | |||
|---|---|---|---|
| PHL (n = 317) | HU (n = 634) | p | |
| Baseline characteristics | |||
| Age at enrolment ≥ 60, n (%) | 172 (54.3%) | 346 (54.6%) | 0.272 |
| Male, n (%) | 221 (69.7%) | 463 (73.0%) | 0.195 |
| Years from diagnosis of PV to enrolment ≥ 5, n (%) | 92 (29.0%) | 161 (25.4%) | 0.148 |
| Prior thrombosis, n (%) | 104 (32.8%) | 221 (34.9%) | 0.915 |
| High risk, n (%) | 202 (63.7%) | 421 (66.4%) | 0.127 |
| Active smoking, n (%) | 65 (20.5%) | 95 (15.0%) | 0.901 |
| Hypertension, n (%) | 131 (41.3%) | 229 (36.1%) | 0.841 |
| Diabetes mellitus, n (%) | 25 (7.9%) | 41 (6.5%) | 0.482 |
| Aspirin use, n (%) | 177 (55.8%) | 359 (56.6%) | 0.393 |
| Oral anticoagulant, n (%) | 19 (6.0%) | 36 (5.7%) | 0.057 |
| BMI categories, n (%) | |||
| Underweight /normal range | 142 (44.8%) | 279 (44.0%) | 0.670 |
| Overweight | 139 (43.8%) | 293 (46.2%) | |
| Obese | 36 (11.4%) | 62 (9.8%) | |
| Follow-up | |||
| Median total follow-up (IQR), months | 29.9 (15.1, 41.0) | 34.7 (24.1, 45.3) | 0.001 |
| Median treatment duration (IQR), months | 25.8 (12.7, 37.3) | 24.0 (12.0, 36.0) | 0.696 |
| Arterial thrombosis | 20 (6.3%) | 15 (2.4%) | 0.002 |
| IR/100 PY (95% CI) | 2.62 (1.69, 4.05) | 0.84 (0.51, 1.39) | 0.001 |
| Myocardial infarction | 1 | 5 | |
| Stroke | 8 | 2 | |
| Transient ischemic attack | 7 | 8 | |
| Peripheral arterial thrombosis | 4 | 0 | |
| Venous thrombosis | 10 (3.2%) | 16 (2.5%) | 0.574 |
| IR/100 PY (95% CI) | 1.29 (0.69, 2.40) | 0.90 (0.55, 1.47) | 0.380 |
| Deep vein thrombosis | 4 | 9 | |
| Superficial vein thrombosis | 6 | 7 | |
PHL Phlebotomy, HU hydroxyurea, IQR interquartile range, IR incidence rate, PY person-years
aTwo randomly sampled HU patients: 1 PHL patient in each matched subset. Matching was done using the nearest neighbor method with replacement and with caliper of width equal to 0.2 of the pooled standard deviation of the logit of PS