Simple Blood Test Predicts Drug Effectiveness in Depression

Deciding which antidepressant is effective could get easier.

A simple finger-prick blood test for C-reactive protein (CRP) could replace the current, sometimes agonizing trial-and-error approach to finding the most effective medication to treat major depression in a specific patient, according to a pilot study at the University of Texas Southwestern.

"Currently, our selection of depression medications is not any more superior than flipping a coin, yet that is what we do,” Madhukar Trivedi MD, (photo) said, "Now we have a biological explanation to guide treatment of depression."

This potential breakthrough is important because as many as one-third of depressed patients don't improve on the first anti-depressant prescribed for them and 40% of patients who try an anti-depressant stop taking it within 3 months, Trivedi found in a previous landmark study of depression.

"This outcome happens because they give up. Giving up hope is really a central symptom of the disease. However, if treatment selection is tied to a blood test and improves outcomes, patients are more likely to continue the treatment and achieve the benefits," Trivedi added, "These findings provide evidence that a biological test can immediately be used in clinical practice."

His randomized controlled study focused on the effectiveness of popular anti-depressants, escitalopram (Lexapro/Forest Laboratories) and bupropion (Wellbutrin/ GlaxoSmithKline). Escitalopram is an SSRI (selective serotonin reuptake inhibitor) and bupropion is an NDRI (norepinephrine-dopamine reuptake inhibitor). CRP is a plasma protein that signals inflammation.

What the Trivedi's team found was that escitalopram as a mono-therapy was most effective for depressed patients whose CRP levels were low (<1 mg/L). They had a 57 % percent remission rate at the end of the 12-week trial. Patients with high CRP levels (>1 mg/L) getting the combination therapy of escitalopram and buproprion had a remission rate of 51%. The high CRP patients had a lower remission rate (31%) on escitalopram alone.

The researchers noted that that the high CRP patients might benefit from the anti-inflammatory effects of bupropion. Why the addition of bupropion is not effective for low CPR patients, who do markedly better on SSRIs "is unclear," the team said.

"Both patients and primary-care providers are very desperately looking for markers that would indicate there is some biology involved in this disease. Otherwise, we are talking about deciding treatments from question-and-answer from the patients, and that is not sufficient," Trivedi added.He is director of the UT Southwestern's Center for Depression Research and Clinical Care.

The researchers said their findings should be "considered preliminary and pilot in nature." Among the limitations cited were the study sample size (106 participants who received the monotherapy or combined therapy) and use of CRP which is an "acute-phase reactant." The study suggested future research could look at SSRI monotherapy vs. bupropion monotherapy.

Can C-reactive protein inform antidepressant medication slection in depressed outpatients? Findings from the CO-MED trial, waspublished in the April issue of Psychoneuroendocrinology

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