Pain
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Higher levels of fear have been shown to partly explain individual differences in placebo analgesic responding. The catechol-O-methyltransferase (COMT) rs4680 Val158Met polymorphism has been associated with both increased placebo analgesia and increased fear-related behavior, in what appears to be inconsistent findings in the literature. The aim of the study was therefore to investigate placebo analgesia and fear-related processes with regard to the COMT genotype, to sort out whether the Met-allele is associated with increased placebo analgesia or increased fear of pain (FOP). ⋯ There was a main effect of the COMT genotype on fear of medical pain (P = 0.032), and Met-allele carriers reported significantly higher fear of medical pain compared with the Val-allele (P = 0.044). We observed no effect of the COMT genotype on mean pain-level report or placebo analgesia. Thus, we conclude that the Met-allele seems to be associated with the negative emotional process of fear, but not with placebo analgesia.
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Randomized Controlled Trial
Effectiveness and costs of a vocational advice service to improve work outcomes in patients with musculoskeletal pain in primary care: A cluster randomised trial (SWAP trial ISRCTN 52269669).
Musculoskeletal pain is a common cause of work absence, and early intervention is advocated to prevent the adverse health and economic consequences of longer-term absence. This cluster randomised controlled trial investigated the effect of introducing a vocational advice service into primary care to provide occupational support. Six general practices were randomised; patients were eligible if they were consulting their general practitioner with musculoskeletal pain and were employed and struggling at work or absent from work <6 months. ⋯ The net societal benefit of the intervention compared with best care was £733: £748 gain (work absence) vs £15 loss (health care costs). The addition of a vocational advice service to best current primary care for patients consulting with musculoskeletal pain led to reduced absence and cost savings for society. If a similar early intervention to the one tested in this trial was implemented widely, it could potentially reduce days absent over 12 months by 16%, equating to an overall societal cost saving of approximately £500 million (US $6 billion) and requiring an investment of only £10 million.
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The comprehensive assessment of pain-related human phenotypes requires combinations of nociceptive measures that produce complex high-dimensional data, posing challenges to bioinformatic analysis. In this study, we assessed established experimental models of heat hyperalgesia of the skin, consisting of local ultraviolet-B (UV-B) irradiation or capsaicin application, in 82 healthy subjects using a variety of noxious stimuli. We extended the original heat stimulation by applying cold and mechanical stimuli and assessing the hypersensitization effects with a clinically established quantitative sensory testing (QST) battery (German Research Network on Neuropathic Pain). ⋯ Unsupervised machine-learning techniques, implemented as emergent self-organizing maps, hinted at subgroups responding to topical application of capsaicin. The distinction among subgroups was based on sensitivity to pressure pain, which could be attributed to sex differences, with women being more sensitive than men. Thus, while UV-B and capsaicin share a major component of heat pain sensitization, they differ in their effects on QST parameter patterns in healthy subjects, suggesting a lack of redundancy between these models.