Correction: Predictors of opioid efficacy in patients with chronic pain: A prospective multicenter observational cohort study.

[This corrects the article DOI: 10.1371/journal.pone.

Predictors of opioid efficacy in patients with chronic pain: A prospective multicenter observational cohort study.

Opioids are increasingly used for treatment of chronic pain. However, they are only effective in a subset of patients and have multiple side effects. Thus, studies using biomarkers for response are highly warranted.