The journal of pain : official journal of the American Pain Society
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Review
Reporting of sample size calculations in analgesic clinical trials: ACTTION systematic review.
Sample size calculations determine the number of participants required to have sufficiently high power to detect a given treatment effect. In this review, we examined the reporting quality of sample size calculations in 172 publications of double-blind randomized controlled trials of noninvasive pharmacologic or interventional (ie, invasive) pain treatments published in European Journal of Pain, Journal of Pain, and Pain from January 2006 through June 2013. Sixty-five percent of publications reported a sample size calculation but only 38% provided all elements required to replicate the calculated sample size. In publications reporting at least 1 element, 54% provided a justification for the treatment effect used to calculate sample size, and 24% of studies with continuous outcome variables justified the variability estimate. Publications of clinical pain condition trials reported a sample size calculation more frequently than experimental pain model trials (77% vs 33%, P < .001) but did not differ in the frequency of reporting all required elements. No significant differences in reporting of any or all elements were detected between publications of trials with industry and nonindustry sponsorship. Twenty-eight percent included a discrepancy between the reported number of planned and randomized participants. This study suggests that sample size calculation reporting in analgesic trial publications is usually incomplete. Investigators should provide detailed accounts of sample size calculations in publications of clinical trials of pain treatments, which is necessary for reporting transparency and communication of pre-trial design decisions. ⋯ In this systematic review of analgesic clinical trials, sample size calculations and the required elements (eg, treatment effect to be detected; power level) were incompletely reported. A lack of transparency regarding sample size calculations may raise questions about the appropriateness of the calculated sample size.
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Randomized Controlled Trial
Can experimentally induced positive affect attenuate generalization of fear of movement-related pain?
Recent experimental data show that associative learning processes are involved not only in the acquisition but also in the spreading of pain-related fear. Clinical studies suggest involvement of positive affect in resilience against chronic pain. Surprisingly, the role of positive affect in associative learning in general, and in fear generalization in particular, has received scant attention. In a voluntary movement paradigm, in which one arm movement (reinforced conditioned stimulus [CS+]) was followed by a painful stimulus and another was not (unreinforced conditioned stimulus [CS-]), we tested generalization of fear inhibition in response to 5 novel but related generalization movements (GSs; within-subjects) after either a positive affect induction or a control exercise (Group = between-subjects) in healthy participants (N = 50). The GSs' similarity with the original CS+ movement and CS- movement varied. Fear learning was assessed via verbal ratings. Results indicated that there was an interaction between the increase in positive affect and the linear generalization gradient. Stronger increases in positive affect were associated with steeper generalization curves because of relatively lower pain-unconditioned stimulus expectancy and less fear of stimuli more similar to the CS-. There was no Group by Stimulus interaction. Results thus suggest that positive affect may enhance safety learning through promoting generalization from known safe movements to novel yet related movements. Improved safety learning may be a central mechanism underlying the association between positive affect and increased resilience against chronic pain. ⋯ We investigated the extent to which positive affect influences the generalization (ie, spreading) of pain-related fear inhibition in response to situations similar to the original, pain-eliciting situation. Results suggest that increasing positive affect in the acute pain stage may limit the spreading of pain-related fear, thereby potentially inhibiting transition to chronic pain conditions.
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Parental responses to their child's pain are associated with the young person's functioning. Psychological flexibility--defined as the capacity to persist with or change behavior, depending on one's values and the current situation, while recognizing cognitive and noncognitive influences on behavior--may provide a basis for further investigating the role of these responses. The Parent Psychological Flexibility Questionnaire (PPFQ) is a promising but preliminary measure of this construct. Parents of 332 young people with pain (301 mothers, 99 fathers, 68 dyads) completed the PPFQ during appointments in a pediatric pain clinic. Initial item screening eliminated 6 of the 31 items. Mothers' and fathers' data were then subjected to separate principal components analyses with oblique rotation, resulting in a 4-factor solution including 17 items, with subscales suggesting Values-Based Action, Pain Acceptance, Emotional Acceptance, and Pain Willingness. The PPFQ correlated significantly with adolescent-rated pain acceptance, functional disability, and depression. Differences were observed between mothers' and fathers' PPFQ scores, in particular, those related to school absence and fears of physical injury. The 17-item PPFQ appears reasonable for research and clinical use and may potentially identify areas for intervention with parents of young people with chronic pain. ⋯ Parent psychological flexibility, as measured by the PPFQ, appears relevant to functioning, depression, and pain acceptance in adolescents with chronic pain. This model may help tie parental responses to adolescent distress and disability and may help clarify the development and maintenance of disability within the context of chronic pain.
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Fatigue is a multidimensional construct that has significant implications for physical function in chronic noncancer pain populations but remains relatively understudied. The current study characterized the independent contributions of self-reported ratings of pain intensity, sleep disturbance, depression, and fatigue to ratings of physical function and pain-related interference in a diverse sample of treatment-seeking individuals with chronic pain. These relationships were examined as a path modeling analysis of self-report scores obtained from 2,487 individuals with chronic pain from a tertiary care outpatient pain clinic. Our analyses revealed unique relationships of pain intensity, sleep disturbance, and depression with self-reported fatigue. Further, fatigue scores accounted for significant proportions of the relationships of both pain intensity and depression with physical function and pain-related interference and accounted for the entirety of the unique statistical relationship between sleep disturbance and both physical function and pain-related interference. Fatigue is a complex construct with relationships to both physical and psychological factors that has significant implications for physical functioning in chronic noncancer pain. The current results identify potential targets for future treatment of fatigue in chronic pain and may provide directions for future clinical and theoretical research in the area of chronic noncancer pain. ⋯ Fatigue is an important physical and psychological variable that factors prominently in the deleterious consequences of pain intensity, sleep disturbance, and depression for physical function in chronic noncancer pain.
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Limited research has examined presurgical risk factors for poor outcomes in children after major surgery. This longitudinal study examined presurgical psychosocial and behavioral factors as predictors of acute postsurgical pain intensity and health-related quality of life (HRQOL) in children 2 weeks after major surgery. Sixty children aged 10 to 18 years, 66.7% female, and their parent/guardian participated in the study. Children underwent baseline assessment of pain (daily electronic diary), HRQOL, sleep (actigraphy), and psychosocial factors (anxiety, pain catastrophizing). Caregivers reported on parental pain catastrophizing. Longitudinal follow-up assessment of pain and HRQOL was conducted at home 2 weeks after surgery. Regression analyses adjusting for baseline pain revealed that presurgery sleep duration (β = -.26, P < .05) and parental pain catastrophizing (β = .28, P < .05) were significantly associated with mean pain intensity reported by children 2 weeks after surgery, with shorter presurgery sleep duration and greater parental catastrophizing about child pain predicting greater pain intensity. Adjusting for baseline HRQOL, presurgery child state anxiety (β = -.29, P < .05) was significantly associated with HRQOL at 2 weeks, with greater anxiety predicting poorer HRQOL after surgery. In conclusion, child anxiety, parental pain catastrophizing, and sleep patterns are potentially modifiable factors that predict poor outcomes in children after major surgery. ⋯ This study addresses an important gap in literature, examining presurgical risk factors for poorer acute postsurgical outcomes in children undergoing major surgery. Knowledge of these factors will enable presurgical identification of children at risk for poorer outcomes and guide further research developing prevention and intervention strategies for these children.