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Comment & Response
July 1, 2020

Questions on a Randomized Clinical Trial of Stellate Ganglion Block for Patients With Posttraumatic Stress Disorder—Reply

Author Affiliations
  • 1RTI International, Research Triangle Park, North Carolina
JAMA Psychiatry. Published online July 1, 2020. doi:10.1001/jamapsychiatry.2020.1822

In Reply On behalf of our coauthors, we thank Dr Stein for his interest in our study, “Effect of Stellate Ganglion Block Treatment on Posttraumatic Stress Disorder Symptoms: A Randomized Clinical Trial.”1 We are pleased to have the opportunity to address his questions.

Regarding the question about why the study enrolled fewer patients than were indicated in our ClinicalTrials.gov registration2: enrollment failed to meet estimates used for the study design in the trial’s first months. An interim sample size reestimation pooling all participants and conducted when the first 82 participants had 8-week data was conducted by analysts blinded to treatment regimen. The observed SD in the Clinician-Administered PTSD Scale for the DSM-5 (CAPS-5) score at 8 weeks was lower (12.4) than that used in the initial sample size estimate (25). Using this revised SD, we estimated that a smaller sample size of 100 to 120 participants (the range that appeared likely with a fixed additional recruitment period of 9 months) would provide reasonable power (80%-95%) to detect a difference of 10 to 15 points in CAPS-5 total symptom severity scores (TSSSs) between the 2 treatment groups. The study sample size was adjusted accordingly.

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