C-reactive Protein May Inform Antidepressant Medication Selection

Baseline C-reactive protein (CRP) levels may be informative to guide treatment selection and improve clinical outcomes for outpatients being treated for depression, according to a study published in the April issue of Psychoneuroendocrinology. In this trial, CRP was the only inflammatory biomarker to predict clinically meaningful treatment outcomes.

Traditionally, antidepressant selection has been based on subjective factors such as cost or patients and/or provider preferences. This trial- and-error approach often requires multiple attempts to achieve adequate symptom control.

The present study involved secondary data analysis of a subset of participants in the Combining Medications to Enhance Depression Outcomes trial. Participants had been randomly assigned to either SSRI monotherapy (n = 51) or bupropion-SSRI combination (n = 55). A predefined CRP threshold of 1 mg/L was used to assess baseline plasma samples. In addition to CRP, serum amyloid P component, and alpha-2-macroglobulin were measured using the Bioplex Pro human- acute-phase 4-plex panel. Depression severity and side effects were the treatment outcomes evaluated weekly or every other week over the 12-week acute phase.

The researchers found that at baseline 37 of 51 participants in the SSRI monotherapy treatment arm had CRP level 1 mg/L or greater, as did 37 of 55 participants in the bupropion-SSRI combination treatment arm. Participants with low CRP levels (less than1 mg/L) performed "markedly better" with SSRI monotherapy than participants with higher CRP levels. In contrast, higher baseline CRP levels (≥1 mg/L) were associated with better outcomes with bupropion- SSRI combination. The researchers say these effects were evident as early as the second week of treatment. The overall remission rate was just over 41 percent. However, using CRP threshold-based assignment (SSRI monotherapy for less than1 mg/L and Bupropion-SSRI for at least1 mg/L) the estimated remission rate with was increased to just over 53 percent, with the number needed to treat of 8.6 to yield one additional remission. No baseline inflammatory marker was associated with side effect burden.

"The lack of moderator effect of serum amyloid P component and alpha-2-macroglobulin is novel and suggests specific role of systemic inflammation in predicting antidepressant treatment response," write the authors led by Manish Jha, from University of Texas Southwestern Medical Center in Dallas. "The implementation of treatment selection based on CRP level can be facilitated in busy clinical practices with the availability of point-of-care testing of CRP."

Takeaway: Baseline CRP levels may improve treatment for outpatients being treated for depression.