Clinical trials show which treatments work for “the average patient,” but we have little ability to predict which treat- ment will work best for any individual patient. QEEG (quantitative EEG) is a method in which a computer program reads EEG tracings and scores them alongcertaindimensions. Acompany called Aspect Medical Systems has been testing a proprietary QEEG system to see if it can predict antidepressant response. In one of the first studies to be pub- lished, 220 depressed patients under- went QEEG testing and then were given open-label Lexapro 10 mg/day. After one week of treatment, all patients were given another QEEG, and a number called the ATR (Antidepressant Treatment Response) index was calculat- ed based on each EEG. Patients were then randomly assigned in a double blind fashion to one of three treatments: a) switch to Wellbutrin, b) add Wellbutrin to Lexapro, or c) continue Lexapro. Patients with ATRs above a cer- tain threshold were 2.4 times as likely to respond to Lexapro as those with low ATRs. On the other hand, when patients with low ATR scores were assigned to Wellbutrin, they were 1.9 times as likely to respond to Wellbutrin as those low ATR patients who had remained on Lexapro. However, low ATR was not use- ful in predicting the response of patients to combination therapy (Leuchter AF et al., Psychiatry Res 2009;169:132-138).
TCPR's Take: If future research vali- dates the ATR score used in this study, then those patients who have high ATRs would be more appropriate for Lexapro treatment (and, by implication, possibly for any SSRI treatment while patients with low ATRs would be appropriate for Wellbutrin. But there are some caveats. The sample was relatively healthy, and any patient who had failed Lexapro or Wellbutrin in the current episode was excluded. The ATR threshold used to predict response was actually modified during the study and then tested on the second half of the patients enrolled. In order to be convincing, this same ATR threshold would have to be tested a pri- ori in a different population of depressed patients. Finally, even if you were itching to start test-driving this system based on this study, you would be unable to obtain the special formula used to com- pute the ATR, because it is a trade secret of Aspect Medical Systems. We’ll have to wait for several more studies before the FDA will approve this diagnostic device. Meanwhile, brief surveys such as the Outcome Questionnaire-45 can also be used to predict treatment response (see October 2008 TCPR).
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