Fibromyalgia patients and healthy volunteers express difficulties and variability in rating experimental pain: a qualitative study.

Background and aims Despite the enormous body of literature spanning more than 50 years describing results of pain experiments, very few have used qualitative methods to explore subjects' thoughts while scoring experimental painful stimuli, and none in the available literature have used qualitative interviews to do so. The current study examined how participants in experimental pain research delineate pain ratings to better understand the unique influences of the experimental setting on pain scores. An additional aim was to highlight how individuals with fibromyalgia and healthy volunteers are differently influenced by characteristics of the experimental setting. Methods This was an inductive, qualitative study in which individual, semi-structured interviews were performed with 31 fibromyalgia patients and 44 healthy volunteers. Participants had taken part in a pain experiment during which a thermode was used to induce painful heat stimuli on two skin areas. There were two primary interview questions analyzed for this report: (1) "Thinking back to when you were getting the heat pain on your leg, what were you thinking about when deciding on your pain score?" and (2) Participants who said that it was difficult to decide on a pain score were asked to, "Describe what made it difficult to choose a number." Thematic analysis was used to generate conceptual categories from textual data and find common themes. Results Three notable differences were found between fibromyalgia patients and healthy volunteers: (1) using current daily pain as a benchmark was seen more in patients, (2) wanting to appear strong in front of the study investigators was more common in healthy volunteers, and (3) becoming mentally fatigued from rating many stimuli was more common for fibromyalgia patients. Thoughts while scoring pain included: (1) comparing with previous or current pain, (2) self-monitoring of one's ability to endure the pain, (3) focusing on the physical aspects of the pain, (4) knowing the experimental setting is safe, (5) focusing on the pain scale as an anchor, and (6) desire to appear strong. Additionally, five difficulties in scoring experimental pain were identified: (1) falling asleep, (2) mentally fatigued, (3) feeling as though they were guessing, (4) having to make a quick decision, and (5) difficulty in being consistent. Conclusions This study provides insights into the thoughts of participants in experimental pain research studies. Participants were distracted and influenced by the experimental setting and some factors differed for fibromyalgia patients versus healthy volunteers. Implications Understanding the ways in which the experimental setting influences pain ratings may help pain researchers better design and interpret studies. Researchers can use these findings to mitigate difficulties for participants in experimental research to add to its validity.