Table 4.
Unadjusted and adjusted hazard ratios for time to maintenance dose for post-initiation factors.
| Post-Initiation Factora (N = 358)b | N (%) ≥1 changec | Median time to first changed | Unadjusted | Adjustedg | ||
|---|---|---|---|---|---|---|
| Hazard Ratioe | P-valuef | Hazard Ratioe | P-valuef | |||
| Change in interacting medication | 48 (13) | 47 (28, 83) | 0.93 (0.70, 1.24) | 0.62 | 1.01 (0.76, 1.34) | 0.95 |
| Change in diet: | ||||||
| Qualitative | 105 (29) | 14 (7, 34) | 0.97 (0.80, 1.17) | 0.73 | 1.00 (0.82, 1.23) | >0.99 |
| Quantitative | 155 (43) | 14 (7, 36) | 0.91 (0.78, 1.07) | 0.24 | 0.98 (0.84, 1.15) | 0.82 |
| Change in weight | 180 (50) | 17 (7, 35) | 0.93 (0.82, 1.06) | 0.26 | 0.97 (0.83, 1.13) | 0.70 |
| Change in alcohol use | 35 (10) | 50 (29, 86) | 0.86 (0.60, 1.23) | 0.42 | 0.96 (0.68, 1.34) | 0.80 |
Post-initiation factors are specified as ordinal time-dependent covariates, with their value equaling the total number of changes in the post-initiation factor reported by a given date.
Both unadjusted and adjusted results are from the same complete-case dataset to improve comparability.
Number (%) of individuals to report at least one change in the given post-initiation factor over the course of follow-up.
Median time (IQR) in days from the initiation of warfarin to the first change experienced by an individual for the given variable.
Hazard ratios are based on the mean estimate from 1,000 bootstrap replications. Hazard ratios can be interpreted as the effect of having one additional change in the given factor on TTM. Hazard ratios less than 1 indicate longer time to maintenance dose; hazard ratios greater than 1 indicate shorter time to maintenance dose.
All P-values are based on the Wald test using the mean and variance of estimates from 1,000 bootstrap replications. Categorical variables were tested jointly.
Adjusted for all baseline factors shown in Table 2, plus visit number to prevent visit frequency from confounding the time-varying covariates.
P < 0.05