Multivariate analysis for the primary and secondary endpoints according to the presenting features in 300 patients with low-risk ET followed with observation or treated with antiplatelet therapy
| . | Total thrombosis . | Arterial thrombosis . | Venous thrombosis . | Major bleeding . | ||||
|---|---|---|---|---|---|---|---|---|
| IRR (95% CI) . | P . | IRR (95% CI) . | P . | IRR (95% CI) . | P . | IRR (95% CI) . | P . | |
| Age older than 40 y | 1.7 (0.8-3.8) | .2 | 1.7 (0.6-4.4) | .3 | 1.7 (0.4-6.9) | .4 | 1.4 (0.4-4.9) | .6 |
| Male sex | 1.9 (0.9-3.9) | .09 | 2.8 (1.5-7.0) | .02 | 0.85 (0.2-3.4) | .8 | 1.1 (0.3-3.4) | .9 |
| Cardiovascular risk factors | 1.7 (0.8-3.7) | .2 | 2.6 (0.98-6.9) | .056 | 0.7 (0.2-2.9) | .7 | 1.0 (0.3-3.3) | .9 |
| Hemoglobin level greater than 140 g/L | 1.1 (0.5-2.3) | .8 | 0.6 (0.3-1.6) | .3 | 3.0 (0.8-11.4) | .1 | 0.6 (0.2-2.0) | .4 |
| Leukocyte count greater than 8.7 × 109/L* | 0.8 (0.4-1.8) | .6 | 0.95 (0.4-2.3) | .9 | 0.7 (0.2-3.1) | .6 | 3.8 (0.8-17.8) | .09 |
| Platelet count greater than 800 × 109/L* | 1.5 (0.7-3.2) | .3 | 1.6 (0.65-4.0) | .3 | 1.0 (0.3-4.1) | .9 | 10.6 (1.6-69.3) | .01 |
| Absence of antiplatelet therapy | 0.9 (0.4-1.8) | .7 | 0.6 (0.2-1.6) | .3 | 1.7 (0.5-6.2) | .4 | — | — |
| Antiplatelet therapy | — | — | — | — | — | — | 1.9 (0.6-6.0) | .3 |
| . | Total thrombosis . | Arterial thrombosis . | Venous thrombosis . | Major bleeding . | ||||
|---|---|---|---|---|---|---|---|---|
| IRR (95% CI) . | P . | IRR (95% CI) . | P . | IRR (95% CI) . | P . | IRR (95% CI) . | P . | |
| Age older than 40 y | 1.7 (0.8-3.8) | .2 | 1.7 (0.6-4.4) | .3 | 1.7 (0.4-6.9) | .4 | 1.4 (0.4-4.9) | .6 |
| Male sex | 1.9 (0.9-3.9) | .09 | 2.8 (1.5-7.0) | .02 | 0.85 (0.2-3.4) | .8 | 1.1 (0.3-3.4) | .9 |
| Cardiovascular risk factors | 1.7 (0.8-3.7) | .2 | 2.6 (0.98-6.9) | .056 | 0.7 (0.2-2.9) | .7 | 1.0 (0.3-3.3) | .9 |
| Hemoglobin level greater than 140 g/L | 1.1 (0.5-2.3) | .8 | 0.6 (0.3-1.6) | .3 | 3.0 (0.8-11.4) | .1 | 0.6 (0.2-2.0) | .4 |
| Leukocyte count greater than 8.7 × 109/L* | 0.8 (0.4-1.8) | .6 | 0.95 (0.4-2.3) | .9 | 0.7 (0.2-3.1) | .6 | 3.8 (0.8-17.8) | .09 |
| Platelet count greater than 800 × 109/L* | 1.5 (0.7-3.2) | .3 | 1.6 (0.65-4.0) | .3 | 1.0 (0.3-4.1) | .9 | 10.6 (1.6-69.3) | .01 |
| Absence of antiplatelet therapy | 0.9 (0.4-1.8) | .7 | 0.6 (0.2-1.6) | .3 | 1.7 (0.5-6.2) | .4 | — | — |
| Antiplatelet therapy | — | — | — | — | — | — | 1.9 (0.6-6.0) | .3 |
ET indicates essential thrombocythemia; and IRR, incidence rate ratio.
Cut points for leukocyte count greater than 10 × 109/L and platelet count greater than 1000 × 109/L were also explored by multivariate analysis but yielded no relevant change in the incidence rate ratios (data not shown).