Non-responders from the prior mail trial and those excluded from mail trial due to lack of a correct mailing address were eligible for the telephone trial.
Starting 20 days after the end of the mail trial, a telephone trial was initiated.
In the mail trial, time zero was defined as the first mailing, using a valid address, to the participant.
In the mail trial, participants were mailed the insurance survey every 2 weeks until the survey was completed or the participant was sent a total of 4 mailings.
Among those who completed surveys, the median (IQR) number of contact attempts was 2 (1, 3) in mail trial and 1 (1, 3) in telephone trial.
There are 332 subjects potentially eligible for the mail trial who were sent either personal (n = 166, 50%) or business (n = 166, 50%) format letters.
There was no significant difference in time to survey completion or response rate between a "personal" versus generic "business" style of envelope in the mail trial, or for a generic telephone message (that used the study name) versus a personalized telephone message (that used the principal investigator's name) for non-responders to the mail trial.
This combined 67% survey completion rate, with individual response rates of 49% in the mail trial and 51% in the telephone trial, compares favorably with other studies [ 10, 22, 45].
Figure 3 shows the Kaplan-Meier curves for time to survey completion for the entire cohort (Panel A), and for the mail trial (Panel B) and the telephone trial (Panel C).
The median (IQR) number of contact attempts was 2 (1, 3) in the mail trial among those participants who completed the survey, which demonstrates that repeated attempts within a single contact modality are needed for survey completion.
