Phenotyping of hand OA based on the location of significant pain could be relevant for patient selection into clinical trials and potentially for future targeting of therapies.
A post-hoc analysis of 106 community-based participants in a RCT of topical betamethasone dipropionate (Diprosone OV) for symptomatic hand OA has identified three common hand pain phenotypes.
All participants had hand pain scores ≥40 out of 100 on VAS at baseline – considered to be significant pain – and radiographic OA.
The three common patterns of pain were pain in both the carpometacarpal (CMC) joint of the thumb and interphalangeal (IP) joints (51.9 %), pain in the IP joints only (26.4 %), and pain in the CMC joint only (15.1 %).
A further 6.6 % of patients had pain in the metacarpophalangeal (MCP) joints but were excluded from analysis due to small numbers.
The Australian study, published in Osteoarthritis and Cartilage Open [link here], found pain in both the CMC and IP joints was associated with higher pain, worse function and stiffness, and higher neuropathic-like pain at baseline compared to those with the CMC only or the IP only pain.
However there was no significant difference between the three groups in total burden of pain over the six-week study period and all three groups showed improvement in all outcomes over six weeks.
There were however some non-significant differences between groups with a higher proportion of the CMC only pain group showing 30% and 50% improvement in VAS (53.3% and 40%), Australian Canadian Osteoarthritis Hand Index (AUSCAN) stiffness (50% and 41.7%), Functional Index for Hand OA (FIOHA) (46.7% and 33.3%) and 50% improvement in AUSCAN function (37.5%) compared to those with the IP only or both CMC and IP pain.
“The IP only group, on the other hand, tended to have highest 30% and 50% improvement in AUSCAN pain (59.3% and 40.7%) and 30% improvement in AUSCAN function (38.5%),” the study said.
The investigators, including Professor Flavia Ciccutini from Monash University, noted the higher clinical burden at baseline and trend for worse prognosis of hand pain and function over 6 weeks in those with CMC and IP pain.
“This may in part be explained by the greater number of joints involved, the longer duration of the disease, and presence of higher neuropathic-like pain in those with both the CMC and IP pain,” they said.
“As different hand pain phenotypes behave differently, the presence of both the CMC and IP pain may reduce the effect of interventions compared to the IP only or CMC only, especially if high levels of neuropathic-like pain are present.”
They said the presence of neuropathic-like pain may reduce the efficacy of other therapies in OA as has been shown in a Dutch study last year [link here].
The Australian study also found the three groups had a gradual reduction in pain from baseline to 4 weeks then an increase in pain from the five-week mark.
The investigators said the significance of the pain level fluctuations warranted further investigations.