Table 2.
Multivariable Cox proportional hazards analysis for overall survival after PV diagnosis by treatments and patient characteristics (n = 820)
| Characteristic* | Model 1 | Model 2 | ||||
|---|---|---|---|---|---|---|
| HR | 95% CI | P | HR | 95% CI | P | |
| Phlebotomy | ||||||
| No | 1.00 | |||||
| Yes | 0.65 | 0.51-0.81 | <.01 | |||
| Phlebotomy intensity (times per year) | 0.71 | 0.65-0.79 | <.01 | |||
| HU PDC (every 10%) | 0.92 | 0.89-0.95 | <.01 | 0.91 | 0.88-0.94 | <.01 |
| Age, y | 1.08 | 1.07-1.10 | <.01 | 1.08 | 1.07-1.10 | <.01 |
| Sex | ||||||
| Female | 1.00 | 1.00 | ||||
| Male | 1.36 | 1.06-1.73 | .01 | 1.37 | 1.07-1.75 | .01 |
| Race | ||||||
| White | 1.00 | 1.00 | ||||
| Nonwhite | 1.18 | 0.79-1.76 | .43 | 1.17 | 0.78-1.74 | .45 |
| Modified Elixhauser score | ||||||
| 0 | 1.00 | 1.00 | ||||
| 1 | 1.19 | 0.88-1.63 | .26 | 1.24 | 0.91-1.68 | .18 |
| ≥2 | 1.46 | 1.10-1.94 | .01 | 1.38 | 1.04-1.84 | .03 |
| Prior thrombosis | ||||||
| No | 1.00 | 1.00 | ||||
| Yes | 1.04 | 0.75-1.45 | .80 | 0.98 | 0.71-1.36 | .91 |
| Disability | ||||||
| No | 1.00 | 1.00 | ||||
| Yes | 1.31 | 0.93-1.85 | .12 | 1.30 | 0.92-1.82 | .13 |
| Low-income subsidy | ||||||
| No | 1.00 | 1.00 | ||||
| Yes | 1.23 | 0.94-1.60 | .13 | 1.18 | 0.90-1.54 | .23 |
| Influenza vaccination within 12 mo prior to PV diagnosis | ||||||
| No | 1.00 | 1.00 | ||||
| Yes | 0.78 | 0.62-0.99 | .04 | 0.79 | 0.63-1.00 | .05 |
*
All variables in the table were simultaneously included in the same model. The only difference between models 1 and 2 was that model 1 included phlebotomy as a binary variable and model 2 included the intensity of phlebotomy (number of phlebotomies each year).