The journal of pain : official journal of the American Pain Society
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Review Meta Analysis
Assay Sensitivity of Pain Intensity Versus Pain Relief in Acute Pain Clinical Trials: ACTTION Systematic Review and Meta-Analysis.
The magnitude of the effect size of an analgesic intervention can be influenced by several factors, including research design. A key design component is the choice of the primary endpoint. The purpose of this meta-analysis was to compare the assay sensitivity of 2 efficacy paradigms: pain intensity (calculated using summed pain intensity difference [SPID]) and pain relief (calculated using total pain relief [TOTPAR]). A systematic review of the literature was performed to identify acute pain studies that calculated both SPIDs and TOTPARs within the same study. Studies were included in this review if they were randomized, double-blind, placebo-controlled investigations involving medications for postsurgical acute pain and if enough data were provided to calculate TOTPAR and SPID standardized effect sizes. Based on a meta-analysis of 45 studies, the mean standardized effect size for TOTPAR (1.13) was .11 higher than that for SPID (1.02; P = .01). Mixed-effects meta-regression analyses found no significant associations between the TOTPAR - SPID difference in standardized effect size and trial design characteristics. Results from this review suggest that for acute pain studies, utilizing TOTPAR to assess pain relief may be more sensitive to treatment effects than utilizing SPID to assess pain intensity. ⋯ The results of this meta-analysis suggest that TOTPAR may be more sensitive to treatment effects than SPIDs are in analgesic trials examining acute pain. We found that standardized effect sizes were higher for TOTPAR compared to SPIDs.
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This study investigated the cross-cultural factor stability and internal consistency of the Revised American Pain Society Patient Outcome Questionnaire (APS-POQ-R), a measure of the quality of postoperative pain management used internationally. We conducted exploratory factor analysis (EFA) of APS-POQ-R data from 2 point prevalence studies comprising 268 and 311 surveys of Danish and Australian medical-surgical patients, respectively. Parallel analysis indicated 4- and 3-factor solutions for Danish and Australian patients, respectively, which accounted for 58.1% and 52.9% of variance. Internal consistency was unsatisfactory among both Danish (Cronbach α = .54) and Australian (Cronbach α = .63) cohorts. There was a high degree of between-group similarity in item-factor loadings of variables coded as "pain experience," but not "pain management." This finding reflected cross-cultural differences in ratings of treatment satisfaction. For Danish patients, satisfaction was associated with the degree of pain severity and activity interference, whereas for Australian patients, satisfaction was associated with their perceived ability to participate in treatment. To facilitate further cross-cultural comparison, we compared our findings with past research conducted in the United States and Iceland. EFA supported the construct validity of the APS-POQ-R as a measure of "pain experience" but indicated that items measuring "pain management" may vary cross-culturally. Findings highlighted the need for further validation of the APS-POQ-R internationally. ⋯ This study revealed the APS-POQ-R as a valid measure of postoperative pain experience for Danish and Australian patients. Measures of patients' perception of pain management were not robust to group differences in treatment expectations and demonstrated cross-cultural instability. Results highlighted the difficulties in establishing stable cross-cultural, cross-population subscales for the APS-POQ-R.
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Allergic contact dermatitis (ACD) is a common condition that can significantly affect the quality of life. Contact with allergens results in delayed hypersensitivity reactions involving T lymphocytes, with associated skin inflammation and spontaneous itch and nociceptive sensations. However, psychophysical studies of these sensations are lacking. In the present study, we sensitized 8 healthy volunteers to squaric acid dibutyl ester (SADBE). Two weeks later, 1 volar forearm was challenged with SADBE, and the other with acetone vehicle control. Subsequently, participants rated the maximal perceived intensity of spontaneous itch, pricking/stinging, and burning every 6 to 12 hours for 1 week, using the generalized Labeled Magnitude Scale. In the laboratory, they judged stimulus-evoked sensations within and outside the chemically treated area. The SADBE- but not the acetone-treated skin resulted in 1) localized inflammation, with spontaneous itch and nociceptive sensations peaking at 24 to 48 hours after challenge, 2) alloknesis, hyperknesis, and hyperalgesia to mechanical stimuli that were reduced or eliminated by anesthetic cooling of the SADBE-treated area and restored on rewarming, suggesting that sensations and dysesthesias are dependent on ongoing peripheral neural activity, and 3) enhanced itch to intradermal injection of histamine, BAM8-22, or β-alanine. This experimental model of T-cell-mediated inflammation may prove useful in evaluating potential treatments of itch from ACD. ⋯ In a model of allergic contact dermatitis, experimentally applied in humans, psychophysical measurements were obtained of persistent, spontaneous itch and enhanced stimulus-evoked itch and pain sensations. These sensory measurements will be useful in the identification of the neural mechanisms underlying inflammatory itch and pain.
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Habituation and sensitization are important features of individual sensitivity to repetitive noxious stimulation and have been investigated in numerous studies. However, it is unclear whether these phenomena vary depending on the site of stimulation. Here we compared short-term and long-term effects of painful heat stimulation on the forehead and limb using an established longitudinal heat pain paradigm performed over 8 consecutive days in 36 healthy volunteers. Participants were randomized into 2 groups; participants received repetitive heat pain stimulation either on the left volar forearm or on the left side of the forehead. Our data show a comparable degree of habituation over the course of 8 days in both groups. However, participants in the trigeminal stimulation group exhibited stronger within-session sensitization (indexed by a higher within-session increase in pain intensity ratings) than those who received the forearm stimulation. Furthermore, over the course of the experiment we found a correlation between habituation and anxiety, showing less habituation in participants with higher trait anxiety scores. Our findings are in line with somatotopic differences in response to painful stimulation and a higher proneness of trigeminal pain to sensitization processes, which might be explained by the biological relevance of the head and facial area for vital functions. The contribution of this sensitivity to the development and maintenance of clinical facial pain and headache disorders warrants further investigation. ⋯ This study uses psychophysical methods to evaluate the differences in long-term habituation and short-term sensitization to heat pain between the trigeminal and spinal systems. We found stronger sensitization for trigeminal compared with nociceptive stimuli on the forearm. The contribution of this sensitivity to clinical pain states warrants further investigation.