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Using Propensity Score Methods to Combine Multiple Data Sources to Compare the Effectiveness of Transcranial Magnetic Stimulation (TMS) with Antidepressant Drug Therapy for Depression
*Annie N Simpson, Medical University of South Carolina Keywords: Propensity Score Methods, Comparative Effectiveness, Depression Transcranial magnetic stimulation (TMS) is FDA cleared for use in depression. Two sham-controlled trials have confirmed its efficacy; however, TMS has not been directly compared to pharmacotherapy. Multiple propensity score methods (matching, weighting, double robust weighting) were used and compared to examine the best way to perform causal analysis on data from two sets of patients from two nonrandomized studies. After TMS patients (TMS study) were propensity score (PS) matched to STAR*D patients (pharmacotherapy study) on baseline characteristics using a 1:1 greedy matching algorithm, an unequal drug resistance distribution in the two populations allowed only 222 of 305 patients to match well on the first attempt. To avoid an incomplete match, propensity score weighting was then attempted and more successful in terms of balance of baseline characteristics between treatment groups. The PS-weighted STAR*D and TMS populations were similar at baseline. Depression score (QIDS-SR) outcomes at six weeks showed the TMS group had a greater clinical improvement (P<0.0001). At six weeks, 53% of TMS patients had no or mild depression versus 38% for STAR*D (p=0.0023).
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