Table 4:
Study participation metrics
| Study participation metric | PAD N=3,493 | No PAD N=11,169 | P value |
|---|---|---|---|
|
| |||
| How was the patient invited to participate? | <.0001 | ||
|
| |||
| Received an email | 1,154 (33.0%) | 4,682 (41.9%) | |
|
| |||
| Received a letter | 721 (20.6%) | 2,346 (21.0%) | |
|
| |||
| Approached in the clinic/hospital | 1,088 (31.1%) | 2,634 (23.6%) | |
|
| |||
| Contacted by telephone | 442 (12.7%) | 1,246 (11.2%) | |
|
| |||
| Used a tablet in the doctor’s office | 71 (2.0%) | 195 (1.7%) | |
|
| |||
| Other | 17 (0.5%) | 65 (0.6%) | |
|
| |||
| Internet participation at randomization | 2,765 (79.2%) | 9,997 (89.5%) | <.0001 |
|
| |||
| Internet participation at last visit | 2,322 (66.5%) | 8,793 (78.7%) | <.0001 |
|
| |||
| Did not complete final visit | 1,258 (39.3.0%) | 3,030 (28.0%) | <.0001 |
|
| |||
| Cumulative percent of actual visits completed | .0005 | ||
|
| |||
| 0% | 136 (3.9%) | 463 (4.1%) | |
|
| |||
| 1–25% | 193 (5.5%) | 547 (4.9%) | |
|
| |||
| 26–50% | 449 (12.9%) | 1,214 (10.9%) | |
|
| |||
| 51–75% | 1,017 (29.1%) | 3,301 (29.6%) | |
|
| |||
| 76–99% | 1,434 (41.1%) | 4,922 (44.1%) | |
|
| |||
| 100% | 264 (7.6%) | 721 (6.5%) | |
|
| |||
| Duration of follow up (Months): mean ± SD | 26.4 +/− 10.1 | 26.4 +/− 9.8 | .9144 |
|
| |||
| Withdrawn consent | 141 (4.0%) | 445 (4.0%) | .8902 |
|
| |||
| EHR data available | 3,493 (100.0%) | 11,168 (100.0%) | 1.000 |
|
| |||
| CMS data available | 1,920 (55.0%) | 5,562 (49.8%) | <.0001 |
|
| |||
| Health plan claims available | 125 (3.6%) | 475 (4.3%) | .0792 |
|
| |||
| Dose switched† | |||
|
| |||
| Randomized to 81 mg | 113 (4.6%) | 358 (4.3%) | .6110 |
|
| |||
| Randomized to 325 mg | 732 (39.7%) | 1,903 (30.7%) | <.0001 |
|
| |||
| Time to first dose switch (months): mean ± SD | 18.3±11.9 | 19.3±11.5 | <.0001 |
|
| |||
| Duration on assigned treatment (days): mean ± SD | 521.4±370.1 | 547.9±365.2 | .0002 |
|
| |||
| Aspirin discontinuation‡ | |||
| Randomized to 81 mg | 170 (6.6%) | 570 (6.5%) | .9951 |
| Randomized to 325 mg | 279 (10.5%) | 843 (10.4%) | .8626 |
Among those still alive at time of study close out
Dose switching is defined as reporting a dose of aspirin different from the randomized dose at one or more postrandomization trial encounters.
Discontinuation is defined as reporting “No” to the trial question “Are you regularly taking aspirin?” at one or more postrandomization trial encounters or never reporting aspirin information during follow-up (missing visits after randomization).
Values are presented as N (%) unless otherwise noted. Trial medication adherence is based on patient report at visits every 3 or 6 months. The End of Study visit was excluded from defining adherence because an observed spike in reports of dose switching at the End of Study visit seemed to reflect participants’ intended dose after trial participation.
Abbreviations: EHR: electronic health record; PAD: peripheral artery disease