An examination of loss to follow-up and potential bias in outcome ascertainment in a study of direct-to-patient telemedicine abortion in the United States

Contraception. 2023 Feb 23:109996. doi: 10.1016/j.contraception.2023.109996. Online ahead of print.

ABSTRACT

OBJECTIVE(S): To examine associations between factors associated with loss to follow-up and effectiveness in the TelAbortion project, which provided medication abortion by direct-to-patient telemedicine and mail in the United States.

STUDY DESIGN: The study population for this descriptive analysis included abortions among participants enrolled in the TelAbortion study with data present in a web-based database tool from November 2018 through September 2021 who were mailed a medication package. The analysis included information on abortions across nine sites. In this analysis, we used generalized estimating equations to examine factors associated with loss to follow-up and effectiveness.

RESULTS: Of the 1,831 abortions included in this analysis, 1,553 (84.8%) were classified as having complete follow-up and 278 (15.2%) were classified as lost to follow-up. In a multivariable analysis, factors significantly associated with loss to follow-up included history of medical abortion, education, gestational age, study site, and whether the TelAbortion was performed pre- or post-COVID-19 onset (p < 0.05). The rate of treatment failure (i.e. abortions resulting in continuing pregnancy or uterine evacuation) reported in this study was 5.1%. The only covariate associated with both loss to follow-up and treatment failure was higher gestational age. However, using gestational age to impute missing abortion outcomes did not substantially change the estimated failure rate.

CONCLUSION(S): Abortions that were lost to follow-up differed substantially from those with complete follow-up, which could bias the effectiveness estimate. However, imputing outcomes based on available and appropriate pre-treatment data did not substantially affect the estimate. This finding is encouraging, although it does not exclude the possibility of bias due to unmeasured factors.

IMPLICATIONS: Significant differences between abortion cases with complete follow-up and those lost to follow-up provide insights into abortion cases that may be at a higher risk for being lost. The low treatment failure rate indicates that the telemedicine provision of medication abortion is effective.

PMID:36841460 | DOI:10.1016/j.contraception.2023.109996