1. 2014;17;E349-E357Examination of Symptom Clusters in Acute and Chronic Pain Patients
   Non-Randomized Study
   David A. Fishbain, MD, Jin Run Gao, PhD, John E. Lewis, PhD, Daniel Bruns, PsyD, Laura J. Meyer, PhD, and John M. Disorbio, EdD.

BACKGROUND: Symptom clusters have not been previously explored in acute pain patients (APPs) and chronic pain patients (CPPs) with non-cancer pain.

OBJECTIVES: The objectives of this study were to determine in CPPs and APPs which somatic and non-somatic symptoms cluster with each other, the number of clusters, and if cluster number and cluster symptom makeup differ by pain level.

STUDY DESIGN: Study sample was 326 APPs and 341 CPPs who had completed a pool of questions that had included current symptom questions other than pain. Symptom cluster analyses were performed on 15 somatic and non-somatic symptoms for APPs and CPPs and for 2 CPP subgroups with moderate and severe pain.

SETTING:  APPs and CPPs were from rehabilitation facilities located in 30 states in all geographical regions of the United States.

RESULTS: APPs had 4 symptom clusters and CPPs had 5. For CPPs, the clusters represented memory, neurological, behavioral, somatic, and autonomic problems. CPPs with moderate and severe pain had 3 and 4 symptom clusters, respectively, and differed in cluster symptom constitution.

LIMITATIONS: Patients selected themselves for study inclusion and were paid for their participation. This could have affected random selection. Lastly, we used the current time definitions of acute pain versus chronic pain (90 days) to separate our patients into these groups. Currently, no consensus exists regarding the optimal time duration to divide acute from chronic.

CONCLUSIONS: APPs and CPPs are characterized by symptom comorbidities that form clusters. In CPPs, cluster number and cluster symptom makeup are affected by pain level. This has implications for clinical practice and future research.