Can early improvement be an indicator of treatment response in obsessive-compulsive disorder? Implications for early-treatment decision-making

In major depression, early response to treatment has been strongly associated with final outcome. We aimed to investigate the ability of early improvement (4 weeks) to predict treatment response at 12 weeks in DSM-IV-defined obsessive-compulsive disorder (OCD) patients treated with serotonin reuptake inhibitors (SRI). We conducted an SRI practical trial with 128 subjects. Inclusion criteria: age range 18e65 years-old, baseline Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) score � 16, and absence of previous adequate pharmacological treatment. Systematic assessments were performed at baseline, 4 and 12 weeks of treatment. Treatment response at 12 weeks was defined as a 35% or greater reduction in baseline Y-BOCS score. Stepwise logistic regression was used to test the relationship between early improvement and treatment response at 12 weeks, taking into account additional potential predictive factors. Different thresholds of early improvement were tested and their predictive power was calculated. Early improvement, defined as a 20% or greater reduction from baseline Y-BOCS score at 4 weeks, predicted response at 12 weeks with 75.6% sensitivity and 61.9% specificity. According to a logistic regression including demographic and clinical features as explaining variables, early improvement was the best predictor of treatment response (OR ¼ 1.05, p < 0.0001). Only 19.8% of patients who did not improve at 4 weeks were responders after 12 weeks. In contrast, 55.3% of the individuals who showed early improvement were responders at 12 weeks (Pearson Chi-Square ¼ 17.06, p < 0.001). Early improvement predicted OCD treatment response with relatively good sensitivity and specificity, such that its role in early decision-making warrants further investigation in wider samples. Trial registration: clinicaltrials.gov Identifier NCT00680602.