Penny Moss

Analysis of meaningful conditioned pain modulation effect in a pain-free adult population.

UNLABELLED Conditioned pain modulation (CPM) encompasses the effects of inhibitory and facilitatory pain modulatory systems and is inefficient in some chronic pain states. A proportion of healthy subjects also exhibit little or no CPM, perhaps suggesting that inherent factors such as gender or genetics may be influential. However, there is no consensus on how best to determine a meaningful CPM effect. This study aimed to determine the proportion of pain-free subjects exhibiting a meaningful CPM effect. Analyses of associations between 5HTTLPR (serotonin transporter-linked polymorphic region) polymorphisms on the serotonin transporter gene (SLC6A4), gender, and CPM effect were also carried out. A total of 125 healthy subjects (47 male; 78 female) underwent pressure pain threshold testing before, during, and after a cold pressor conditioning stimulus. A buccal cell sample was collected for analysis of 5HTTLPR genotype. Meaningful CPM effect was determined as an increase in pressure pain threshold values from baseline greater than the inherent error of measurement, calculated as 5.3%. During the conditioning stimulus, 116 subjects (92.8%) exhibited a CPM effect whereas 9 did not. CPM effect did not differ significantly between genders or between 5HTTLPR genotypes. This provides a clear basis on which to determine the proportion of patients with a chronic pain disorder that exhibit a meaningful CPM effect. PERSPECTIVE This study proposes a method for calculating meaningful CPM effect and reports the proportion and magnitude of effect elicited in a large sample. Associations between CPM, gender, and genotype were also analyzed. Clarification of normal CPM response may help to elucidate the mechanisms driving CPM inefficiency in chronic pain.

Subjects with Knee Osteoarthritis Exhibit Widespread Hyperalgesia to Pressure and Cold

Hyperalgesia to mechanical and thermal stimuli are characteristics of a range of disorders such as tennis elbow, whiplash and fibromyalgia. This study evaluated the presence of local and widespread mechanical and thermal hyperalgesia in individuals with knee osteoarthritis, compared to healthy control subjects. Twenty-three subjects with knee osteoarthritis and 23 healthy controls, matched for age, gender and body mass index, were recruited for the study. Volunteers with any additional chronic pain conditions were excluded. Pain thresholds to pressure, cold and heat were tested at the knee, ipsilateral heel and ipsilateral elbow, in randomized order, using standardised methodology. Significant between-groups differences for pressure pain and cold pain thresholds were found with osteoarthritic subjects demonstrating significantly increased sensitivity to both pressure (p = .018) and cold (p = .003) stimuli, compared with controls. A similar pattern of results extended to the pain-free ipsilateral ankle and elbow indicating widespread pressure and cold hyperalgesia. No significant differences were found between groups for heat pain threshold, although correlations showed that subjects with greater sensitivity to pressure pain were also likely to be more sensitive to both cold pain and heat pain. This study found widespread elevated pain thresholds in subjects with painful knee osteoarthritis, suggesting that altered nociceptive system processing may play a role in ongoing arthritic pain for some patients.

Cold Pain Threshold Identifies a Subgroup of Patients With Knee Osteoarthritis That Present With Multimodality Hyperalgesia and Elevated Pain Levels

Objectives: Cold hyperalgesia has been established as an important marker of pain severity in a number of conditions. This study aimed to establish the extent to which patients with knee osteoarthritis (OA) demonstrate widespread cold, heat, and pressure hyperalgesia. OA participants with widespread cold hyperalgesia were compared with the remaining OA cohort to determine whether they could be distinguished in terms of hyperalgesia, pain report, pain quality, and physical function. Methods: A total of 80 participants with knee OA and 40 matched healthy, pain-free controls participated. OA participants completed a washout of their usual medication. Quantitative sensory testing was completed at 3 sites using standard methods. Cold pain threshold (CPT) and heat pain thresholds (HPT) were tested using a Peltier thermode and pressure pain thresholds (PPT) using a digital algometer. All participants completed the short-form health survey questionnaire and OA participants completed the PainDETECT, Western Ontario and McMaster Universities Osteoarthritis Index of the Knee (WOMAC), and pain quality assessment scale questionnaires. Results: OA participants demonstrated widespread cold hyperalgesia (P<0.0001), had lower PPT at the index knee (P<0.0001) compared with controls and reported decreased physical health on the SF-36 (P=0.01). The OA subcohort with high global CPT (≥12.25°C) exhibited multimodality sensitization compared with the remaining OA cohort (PPT P<0.0001; CPT P<0.0001; HPT P=0.021 index knee). This group also reported increased pain, decreased function, and more features of neuropathic pain. Discussion: This study identified a specific subgroup of patients with knee OA who exhibited widespread, multimodality hyperalgesia, more pain, more features of neuropathic pain, and greater functional impairment. Identification of patients with this pain phenotype may permit more targeted and effective pain management.

Identifying culturally appropriate strategies for coronary heart disease secondary prevention in a regional Aboriginal Medical Service

Aboriginal Australians experience high rates of coronary heart disease (CHD) at an early age, highlighting the importance of effective secondary prevention. This study employed a two-stage process to evaluate CHD management in a regional Aboriginal Medical Service. Stage 1 involved an audit of 94 medical records of clients with documented CHD using the Audit and Best Practice in Chronic Disease approach to health service quality improvement. Results from the audit informed themes for focus group discussions with Aboriginal Medical Service clients (n=6) and staff (n=6) to ascertain barriers and facilitators to CHD management. The audit identified that chronic disease management was the focus of appointments more frequently than in national data (P<0.05), with brief interventions for lifestyle modification occurring at similar or greater frequency. However, referrals to follow-up support services for secondary prevention were lower (P<0.05). Focus groups identified psychosocial factors, systemic shortcomings, suboptimal medication use and variable awareness of CHD signs and symptoms as barriers to CHD management, whereas family support and culturally appropriate education promoted health care. To optimise CHD secondary prevention for Aboriginal people, health services require adequate resources to achieve best-practice systems of follow up. Routinely engaging clients is required to ensure services meet diverse community needs.

Exercise-induced hypoalgesia in women with varying levels of menstrual pain

Abstract Background and aims: Exercise-induced hypoalgesia (EIH) is a well-established phenomenon in pain-free individuals that describes a decrease in pain sensitivity after an acute bout of exercise. The EIH response has been demonstrated to be sub-optimal in the presence of persisting pain. Menstrual pain is a common recurrent painful problem with many women experiencing high levels of pain each cycle. However, the EIH response has not been examined in a cohort of women with high levels of menstrual pain. This research aimed to examine whether EIH manifests differently in women with varying levels of menstrual pain. The primary hypothesis was that women with high levels of menstrual pain would demonstrate compromised EIH. Secondary aims were to explore relationships between EIH and emotional state, sleep quality, body mass index (BMI) or physical activity levels. Methods: Pressure pain thresholds (PPT) were measured in 64 participants using a digital handheld algometer before and after a submaximal isometric-handgrip exercise. EIH index was compared between low (VAS 0–3), moderate (VAS 4–7) and high (VAS 8–10) pain groups, using a linear mixed model analysis with participant as a random effect, and site, menstrual pain category and the interaction between the two, as fixed effects. Results: EIH was consistently induced in all groups. However, there was no statistically significant difference between the pain groups for EIH index (p=0.835) or for any co-variates (p>0.05). Conclusions: EIH was not found to differ between women who report regular low, moderate or high levels of menstrual pain, when measured at a point in their menstrual cycle when they are pain free. Implications: This study provides insight that EIH does not vary in women with differing levels of menstrual pain when they are not currently experiencing pain. The current findings indicate that, although menstrual pain can involve regular episodes of high pain levels, it may not be associated with the same central nervous system dysfunctions as seen in sustained chronic pain conditions.

Subjects with Knee Osteoarthritis Exhibit Widespread Hyperalgesia toPressure and Cold

Hyperalgesia to mechanical and thermal stimuli are characteristics of a range of disorders such as tennis elbow, whiplash and fibromyalgia. This study evaluated the presence of mechanical and thermal hyperalgesia in individuals with knee osteoarthritis (OA), compared to healthy control subjects. Twenty-three subjects with knee OA and 23 healthy controls, matched for age, gender and BMI, were recruited for the study. Volunteers with any additional chronic pain conditions were excluded. Pain thresholds to pressure (PPT), cold (CPT) and heat (HPT) were tested at the knee, ipsilateral heel and elbow, in randomized order, using standardised methodology. Significant between-groups differences for PPT and CPT were found: OA subjects demonstrated significantly increased sensitivity to both pressure (p=0.018) and cold (p=0.003), but not to heat (p=0.167) stimuli, compared with controls. A similar pattern of results extended to the pain-free ipsilateral ankle and elbow indicating widespread pressure and cold hyperalgesia. This study found widespread elevated pain thresholds in subjects with painful knee OA, suggesting that altered nociceptive system processing may play a role in ongoing arthritic pain for some patients.

Differences in Quantitative Sensory Testing and Functional Testing Between Patients with Osteoarthritis and Matched Controls

Background Osteoarthritis (OA) is acknowledged as a complex, heterogeneous pathology. It has been suggested that new assessment approaches are needed to evaluate OA patients so that treatment can be targeted optimally. Objectives This study aimed to investigate whether subjects with knee OA exhibit higher levels of sensory hyperalgesia and functional impairment, as measured using quantitative sensory test (QST) measures and standardised functional tests, than a cohort of healthy age and gender-matched controls. The relationship between quantitative tests and a self-report measure of quality of life was also investigated. Methods 40 volunteers with painful knee OA were recruited in addition to 40 healthy volunteers, matched by gender and five-year age band (16 male: 24 female, mean age 64 years both groups). OA subjects were withdrawn from their usual analgesics / NSAIDs during testing. All subjects initially completed a SF36 Quality of Life questionnaire. Functional status was assessed using the aggregated locomotion function (ALF) score [1]: total time taken to complete three tasks – 3m chair transfer, 8m walk and a standardised flight of stairs. QST was applied at both knees and the unaffected right elbow with standard methods used and mean of 3 trials analysed. Cold and heat detection and pain thresholds (CDT, CPT, HDT, HPT) were tested using a peltier thermode (Medoc, Israel) and pressure pain thresholds (PPT) using a digital algometer (Somedic, AB). Results There was a significant group difference in ALF score (p<.001 all tasks) with OA subjects performing the tasks on average 37% slower than controls. There was a significant group difference in CPT at all sites (p<.001) with OA subjects exhibiting a mean CPT of 11ºC (SD 7.8ºC) compared with controls (mean CPT 2.7ºC (SD 4.1ºC). PPT was reduced at all sites in OA patients, although only significantly at the OA knee (p=.003). There was no group difference in HPT or HDT at any site. In contrast, CDT was significantly less sensitive in the OA knee (p=.021) but not at other sites. SF36 scores showed no significant group difference in Mental Component (p=.961) although there was a significant difference in Physical Component (p=.048). Conclusions When compared with age and gender-matched controls, subjects with knee OA demonstrated higher levels of cold and mechanical hyperalgesia which spread beyond the affected joint, associated with lower levels of physical function. QST and functional tests may therefore be useful tools with which to evaluate OA patients in the clinical setting and in clinical trials. References McCarthy CJ, Oldham JA (2004): The reliability, validity and responsiveness of an aggregated locomotion function score in patients with osteoarthritis of the knee. Rheumatology 43(4): 514-517 Acknowledgements Study supported by an Investigator Initiated Research grant from Merck, Sharp and Dohme. Disclosure of Interest T. Wright Shareholder of: Algometron Pty Ltd - company developing a new QST measure, Grant/research support from: Investigator Initiated Research grant from Merck, Sharp and Dohme., P. Moss Shareholder of: Algometron Pty Ltd - company developing a new QST measure, Grant/research support from: Investigator Initiated Research grant from Merck, Sharp and Dohme., R. Will Grant/research support from: Investigator Initiated Research grant from Merck, Sharp and Dohme., H. Benson Shareholder of: Algometron Pty Ltd - company developing a new QST measure, Grant/research support from: Investigator Initiated Research grant from Merck, Sharp and Dohme.