Presented at the 2013 AAPM Annual Meeting « Back

SF-36 Questionnaire May Predict High Placebo Response in Evaluating the Efficacy of Treatment Of Chronic Pain

Mi Rim Kim, MD PhD, kimm4@mail.nih.gov¹, Joe Galen, MD¹, Janet Rowan, RN¹, Leorey Saligan, RN PhD CRNP¹, Christina Yetter, BS², Moinuddin Hassan, PhD³, Koki Fukuhara, PhD¹, (1) National Institutes of Health, Bethesda, Maryland, (2) University of Pittsburgh School of Nursing, Pittsburgh, Pennsylvania, (3) Federal Drug Administration, Bethesda, Maryland

Introduction: It might be crucial to exclude subjects who are highly responsive to placebo in the evaluation of pain treatment. Unexpectedly, we have observed significant improvement of pain and clinical symptoms with placebo in a drug trial of Complex Regional Pain Syndrome (n=17). In this study, 50% of the subjects in the placebo group (n=8) showed significant decrease in Numerical Rating Scale (≥2) after 5 weeks of placebo. To understand the characteristics of these strong placebo responders, we compared two groups. There was no significant difference in age, duration of the disease, NRS, VAS, McGill pain questionnaire score, range of motion of joints, edema, skin temperature, allodynia, hyperalgesia, and current and pain perception threshold at baseline. However, among the monthly SF-36 questionnaire score, bodily pain score was significantly higher in the subjects who showed strong placebo effect (34.1 vs.23.6; p=0.02, range; 28.7 to 41.8 vs. 19.9 to 24.9). Also, vitality score was higher in placebo responders without statistical significance (43.3 vs. 34.4; p=0.09, range; 33.4 to 52.1 vs. 29.2 to 37.5). Especially, there was no overlap in bodily pain score between two groups. Strong placebo effect can be predicted in the subjects with SF-36 bodily pain score greater than 25. These results suggest that SF-36 score (bodily pain, vitality) should be matched between placebo and treatment group in clinical trial. Also it can be used as a useful tool for checking randomization. Further study will be needed to validate these findings in patients with other types of chronic pain.

Funding: None