Objectives: To assess the value of the concept of mixed pain by investigating its acceptance and interpretation by health care professionals and the differential characteristics in patients with mixed pain.
Materials and methods: Data from 5024 patients with pain from 551 sites in Primary Care and Orthopedics settings were analyzed in this cross-sectional study. Pain characteristics, other factors influencing pain, health care-related data and health-related quality of life were summarized and compared among 3 groups of patients according to the type of pain (nociceptive, neuropathic, or mixed), as assigned by the investigators after considering the pathophysiological mechanisms involved.
Results: Pain was of mixed pathophysiology in most patients (59.3%; 95% confidence interval [CI], 59.2%-59.5%), followed by nociceptive (31.8%; 95% CI, 31.6%-32.0%) and neuropathic pathophysiology (8.9%; 95% CI, 8.8%-9.1%). Patients with mixed pain had pain in >1 site more frequently than the other groups. Spinal conditions was the attributed cause of pain in >80% of patients with mixed pain, whereas nonspinal osteoarthritis represented almost a third. Patients with mixed pain showed a greater clinical complexity than the remaining patients, as they reflected: more comorbidities, adverse psycho-social factors, health care resource utilization, undertreatment, and perceived difficulties in patient management, but less perceived effectiveness of treatments and a lower health-related quality of life.
Discussion: An independent category in the pathophysiological classification of pain is justified based on the differential characteristics of patients with mixed pain, although conceptualization of mixed pain should be improved. Increasing referrals to other specialists or implementing chronic pain management programs would seem advisable.
Conclusions: Patients with mixed pain showed more clinical complexity than patients with other types of pain. The consideration of mixed pain as an independent pathophysiological category may be justifiable on empirical clinical grounds.