Early drop-outs, late drop-outs and completers: differences in the continuation phase of a clinical trial.

The purpose of this study was to assess the differences between early (EDs), late drop-outs (LDs) and completers in the continuation phase of a clinical trial. The authors studied 119 outpatients who were treatment responders in an 8-week open trial with fluoxetine 20 mg/day, and who were then enrolled in a 26-week clinical trial comparing the efficacy of fluoxetine versus fluoxetine and cognitive behavior therapy (CBT). Patients were assessed using the Structured Clinical Interview for DSM-III-R-Axis I (SCID-Patient Edition), Hamilton Depression Rating Scale (HAMD-17) and the following self-rated scales: Beck Depression Inventory (BDI), Beck Hopelessness Scale (BHS), Anxiety Sensitivity Index (ASI) and the Symptom Questionnaire (SQ) prior to starting the 26-week continuation phase. We defined 'EDs' as patients who dropped out either at or prior to Visit 2 (which was at 2 months into the 6-month continuation phase); those dropping out at Visit 3 or later were defined as 'LDs' (ED < or = 2 months and LD > 2 months). The Kruskal-Wallis and the Mann-Whitney U tests were used for data analysis. Of the 119 outpatients, 83 were completers (mean age: 42.1 +/- 9.0 years, 46 [55%] women, age of onset of major depressive disorder [MDD] = 24.3 +/- 12.5 years), 11 were EDs (mean age: 38.1 +/- 13.0 years, 4 [36%] women, age of onset of MDD = 22.0 +/- 11.1 years) and 25 were LDs (mean age: 35.2 +/- 10.4 years, 12 [48%] women, age of onset of MDD = 24.6 +/- 11.6 years). LDs were significantly younger than completers (P<.01). There was no significant difference in age between EDs and LDs, nor between EDs and completers. EDs and completers were depressed for a longer period of time compared to LDs (P<.05). EDs also had significantly greater overall impairment in social adjustment compared to completers (P<.05). Our data suggest that LDs are significantly younger than completers, although age is not a predictor between EDs and LDs. Further, EDs and completers are depressed for a longer duration than LDs, and EDs have significantly greater social impairment compared to completers. Our study identified some patient characteristics significantly associated with dropping out of a long-term clinical trial.