Central sensitization is common in patients with hand osteoarthritis (OA), possibly representing a potential treatment target, according to research published in Arthritis and Rheumatology.
Researchers examined data collected in the Nor-Hand Study (NCT03083548), an observational, hospital-based cohort study of patients with hand OA, to assess the prevalence of both central and peripheral sensitization and the relationship between sensitization and hand pain severity.
Eligible patients were between ages 40 and 70 years and had the presence of OA in ≥1 interphalangeal or thumb base joint. Researchers assessed self-reported hand pain using the Numerical Rating Scale (NRS) questionnaire and the pain subscale of the Australian/Canadian Osteoarthritis Hand Index (AUSCAN). They conducted quantitative sensory testing, including pressure pain threshold and mechanical temporal summation as well.
In total, 282 patients were eligible for analysis. Radiographically detected OA ranged from mild to severe; as reported by both the NRS and AUSCAN questionnaires, pain severity was above the acceptable symptom state in 33% and 52% of the patient population, respectively; however, only 41 patients received ≥1 oral and/or topical analgesic on a daily basis (acetaminophen, nonsteroidal anti-inflammatory drugs, or opioids or opioid-like drugs).
Researchers identified a consistent trend of increasing self-reported pain as pressure pain thresholds decreased in the painful and nonpainful finger joints. Those participants in the lowest pressure pain threshold tertile reported average NRS scores 1 point (painful finger joint) and 1.2 points (nonpainful finger joint) higher; AUSCAN pain scores were 1 point (painful finger joint) and 1.4 points (nonpainful finger joint) higher than those in the highest tertiles.
Adjusted analyses found an independent association between lowest-tertile pressure pain threshold and pain severity in NRS only (adjusted β = 0.7 and β = 0.9) for the painful and nonpainful finger joints, respectively. On repeated analyses, with pressure pain thresholds at the finger joints as a continuous variable, significant inverse associations were noted with NRS, but not AUSCAN, pain scores.
On average, patients with mechanical temporal summation reported a 1- and 1.1-point higher pain score on NAS and AUSCAN, respectively, compared with patients without mechanical temporal summation. The adjusted analysis identified an association between mechanical temporal summation and pain severity in NRS only.
Study limitations included the cross-sectional design, data weakening by participants who responded late to the questionnaires, and missing data on the use of analgesic medications on the day that patients answered the questionnaires or underwent quantitative sensory testing.
“We found that central sensitization is common in individuals with hand OA, and we demonstrated a relationship between higher sensitivity and higher self-reported hand pain,” the researchers concluded. “Future studies may explore the sensitization-associated pain phenotype longitudinally as a possible risk factor for prognosis, as well as a potential predictor for treatment outcomes.”
Steen Pettersen P, Neogi T, Magnusson K, et al. Peripheral and central sensitization of pain in individuals with hand osteoarthritis and associations with self-reported pain severity [published online February 11, 2019]. Arthritis Rheumatol. doi: 10.1002/art.40850