Methods to limit attrition in longitudinal comparative effectiveness trials: lessons from the Lithium Treatment – Moderate dose Use Study (LiTMUS) for bipolar disorder

Background High attrition rates, which occur frequently in longitudinal clinical trials of interventions for bipolar disorder, limit the interpretation of results.

Purpose The aim of this article is to present design approaches that limited attrition in the Lithium Treatment – Moderate dose Use Study (LiTMUS) for bipolar disorder.

Methods LiTMUS was a 6-month randomized, longitudinal multisite comparative effectiveness trial that enrolled bipolar participants who were at least mildly ill. Participants were randomized to either low to moderate doses of lithium or no lithium; other treatments needed for mood stabilization were administered in a guideline-informed, empirically supported, and personalized fashion to participants in both treatment arms.

Results Components of the study design that may have contributed to low attrition (16%) among 283 participants randomized included the use of (1) an intent-to-treat design, (2) a randomized adjunctive single-blind design, (3) participant reimbursement, (4) assessment of intent to attend the next study visit (included a discussion of attendance obstacles when intention was low), (5) quality care with limited participant burden, and (6) target windows for study visits.

Limitations The relationships between attrition and effectiveness and tolerability of treatment have not been analyzed yet.

Conclusions These components of the LiTMUS design may have limited attrition and may inform the design of future randomized comparative effectiveness trials among similar patients and those from other difficult-to-follow populations.