Influence and stability of pain scale anchors for an investigation of cold pressor pain tolerance

A Novel Movement-Evoked Pain Provocation Test for Older Adults With Persistent Low Back Pain: Safety, Feasibility, and Associations With Self-reported Physical Function and Usual Gait Speed

OBJECTIVES

Low back pain (LBP) is highly prevalent and disabling for older adults. Movement-evoked pain is an emerging measure that may help to predict disability; but is not currently a part of geriatric LBP clinical care. This study tested the safety and feasibility of a new Movement-Evoked Provocation Test for Low Back Pain in Older Adults (MEPLO). We also compared associations between movement-evoked pain via 2 different scoring methods and disability-associated outcomes.

MATERIALS AND METHODS

Thirty-nine older adults with persistent LBP provided baseline recalled and resting pain ratings, self-reported physical function, and usual gait speed. Participants then completed MEPLO, involving 4 tasks essential for functional independence: chair rises, trunk rotation, reaching, and walking. Movement-evoked pain was then quantified using the traditional change score (delta) method of pain premovement to postmovement; and also, a new aggregate method that combines pain ratings after the 4 tasks.

RESULTS

No safety or feasibility issues were identified. Compared with the delta score, the aggregate score was more strongly associated with self-reported physical function (beta: -0.495 vs. -0.090) and usual gait speed (beta: -0.450 vs. -0.053). Similarly, the aggregate score was more strongly associated with self-reported physical function than recalled and resting pain (beta: -0.470, -0.283, and 0.136, respectively).

DISCUSSION

This study shows the safety and feasibility of testing movement-evoked pain in older adults with persistent LBP, and its potential superiority to traditional pain measures. Future studies must validate these findings and test the extent to which MEPLO is implementable to change with geriatric LBP standard of care.

Measuring pain and nociception: Through the glasses of a computational scientist. Transdisciplinary overview of methods

In a healthy state, pain plays an important role in natural biofeedback loops and helps to detect and prevent potentially harmful stimuli and situations. However, pain can become chronic and as such a pathological condition, losing its informative and adaptive function. Efficient pain treatment remains a largely unmet clinical need. One promising route to improve the characterization of pain, and with that the potential for more effective pain therapies, is the integration of different data modalities through cutting edge computational methods. Using these methods, multiscale, complex, and network models of pain signaling can be created and utilized for the benefit of patients. Such models require collaborative work of experts from different research domains such as medicine, biology, physiology, psychology as well as mathematics and data science. Efficient work of collaborative teams requires developing of a common language and common level of understanding as a prerequisite. One of ways to meet this need is to provide easy to comprehend overviews of certain topics within the pain research domain. Here, we propose such an overview on the topic of pain assessment in humans for computational researchers. Quantifications related to pain are necessary for building computational models. However, as defined by the International Association of the Study of Pain (IASP), pain is a sensory and emotional experience and thus, it cannot be measured and quantified objectively. This results in a need for clear distinctions between nociception, pain and correlates of pain. Therefore, here we review methods to assess pain as a percept and nociception as a biological basis for this percept in humans, with the goal of creating a roadmap of modelling options.

Prediction of pain responses to subsequent cold pressor test via baseline heart rate variability in healthy adults

BACKGROUND

Baseline heart rate variability (HRV) that reflects parasympathetic nervous system (PNS) activity may serve as an objective, physiological index of pain assessment, but more research is warranted to examine the link between HRV and laboratory pain responses. This study examined whether baseline HRV would predict pain responses to subsequent cold pressor test (CPT) in healthy adults.

METHODS

One hundred twenty-three participants completed resting HRV assessment and CPT consisting of immersing their right hand into a cold-water bath for a maximum of 2 minutes. Pain threshold and pain rating were assessed during CPT. Completion status of CPT, defined as completing CPT or terminating CPT before 2 minutes, was recorded as an additional laboratory pain measure. Pearson's correlation analysis was performed to examine the link between HRV and pain responses, whereas regression analysis was performed to test the prediction of pain responses via baseline HRV.

RESULTS

HF-HRV_log , which reflects PNS activity, was significantly associated with the CPT completion status (r = 0.23, p = 0.01), but not significantly associated with pain threshold (r = 0.17, p = 0.06) nor pain rating (r = -0.11, p = 0.24). HF- HRV_log was found to be a significant predictor of the CPT completion status (B = 0.53, p = 0.013).

CONCLUSIONS

Baseline HF- HRV_log may serve as an objective, physiological index to predict laboratory pain responses, and completion status of laboratory pain tests, such as CPT, may be used as a laboratory pain measure to capture important individual differences in pain processing.

Preoperative Education for Less Outpatient Pain after Surgery (PELOPS trial) in orthopedic patients-study protocol for a randomized controlled trial

Background

Successful pain management after outpatient surgery requires proper education leading to correct decisions on the analgesics use at home. Despite different strategies adopted, up to ½ of patients receive little or no information about the treatment of postoperative pain, 1/3 of them are not able to follow postoperative analgesia instructions. This leads to higher rates of unmet needs in pain treatment, post-discharge emergency calls, and readmissions. Structured educational interventions using psychological empowering techniques may improve postoperative pain management. We hypothesize that preoperative education on use of an improved pain scale to make correct pain management decisions will improve the quality of post-operative pain management at home and reduce analgesics-related side effects.

Methods

A total of 414 patients scheduled for an outpatient orthopedic surgery (knee/shoulder arthroscopic interventions) are included in this randomized (1:1) controlled trial. Patients in the control arm receive standard information on post-discharge pain management. Patients in the experimental arm receive structured educational intervention based on the rational perception of postoperative pain and discomfort (anchoring and improved pain scale), and the proper use of analgesics. There is no difference in post-discharge analgesics regimen in both arms. Patients are followed for 30 days post-discharge, with the primary outcome expressed as total pain relief score at 5 days. Secondary outcomes include the incidence of severe pain during 30 days, changes in sleep quality (Pittsburg Sleep Quality Assessment), and patients’ perception of postoperative pain management assessed with the International Pain Outcomes questionnaire at day 30 post-discharge.

Discussion

The developed intervention, based on an improved pain scale, offers the advantages of being non-surgery-specific, is easily administered in a short amount of time, and can be delivered individually or in-group, by physicians or nurses.

Trial registration

ClinicalTrials.govNCT03754699. Registered on November 27, 2018.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-022-06387-6.

No Evidence of Altered Reactivity to Experimentally Induced Pain Among Regular Cannabis Users

OBJECTIVES

Recent years have seen an increase in the adoption of cannabinoid medicines, which have demonstrated effectiveness for the treatment of chronic pain. However, the extent to which frequent cannabis use (CU) influences sensitivity to acute pain has not been systematically examined. Such a determination is clinically relevant in light of hypersensitivity to pain associated with prolonged use of other analgesics such as opioids, and reports of increased pain sensitivity to experimentally induced pain during acute cannabis intoxication. This study explored differences in measures of pain intensity and tolerance. The authors hypothesized that individuals who report frequent CU would demonstrate greater experimental pain sensitivity.

MATERIALS AND METHODS

Frequent cannabis users (≥3× per week; n=40) and nonusers (n=40) were compared on pain sensitivity, pain tolerance, and pain intensity in response to a cold-pressor task. Group differences were examined.

RESULTS

Frequent CU was not associated with hyperalgesia as cannabis users and nonusers did not exhibit differences on measures of pain tolerance (t (78)=-0.05; P=0.96), sensitivity (t (78)=-0.83; P=0.41), or intensity (t (78)=0.36; P=0.72).

DISCUSSION

Frequent cannabis users did not demonstrate hyperalgesia. This finding should help to inform evaluations of the relative harms and benefits of cannabis analgesic therapies.

Challenges and opportunities in translational pain research - An opinion paper of the working group on translational pain research of the European pain federation (EFIC)

For decades, basic research on the underlying mechanisms of nociception has held promise to translate into efficacious treatments for patients with pain. Despite great improvement in the understanding of pain physiology and pathophysiology, translation to novel, effective treatments for acute and chronic pain has however been limited, and they remain an unmet medical need. In this opinion paper bringing together pain researchers from very different disciplines, the opportunities and challenges of translational pain research are discussed. The many factors that may prevent the successful translation of bench observations into useful and effective clinical applications are reviewed, including interspecies differences, limited validity of currently available preclinical disease models of pain, and limitations of currently used methods to assess nociception and pain in non-human and human models of pain. Many paths are explored to address these issues, including the backward translation of observations made in patients and human volunteers into new disease models that are more clinically relevant, improved generalization by taking into account age and sex differences, and the integration of psychobiology into translational pain research. Finally, it is argued that preclinical and clinical stages of developing new treatments for pain can be improved by better preclinical models of pathological pain conditions alongside revised methods to assess treatment-induced effects on nociception in human and non-human animals. Significance: For decades, basic research of the underlying mechanisms of nociception has held promise to translate into efficacious treatments for patients with pain. Despite great improvement in the understanding of pain physiology and pathophysiology, translation to novel, effective treatments for acute and chronic pain has however been limited, and they remain an unmet medical need.

"Sometimes you wonder, is this really true?": Clinician assessment of patients' subjective experience of pain

BACKGROUND

Pain is a subjective experience that must be translated by clinicians into an objective assessment to guide intervention.

OBJECTIVE

To understand how patients' subjective experience of pain is translated by primary care clinicians into an objective clinical assessment of pain to effectively guide intervention.

METHODS

We conducted nine multidisciplinary focus groups with a combined total of 60 Veteran affair (VA) primary care providers and staff from two large VA medical centers in California and Oregon. We used content analysis methods to identify key themes pertaining to clinical assessment of a subjective experience.

RESULTS

We present four emergent themes. Theme 1: Pain is a highly individualized and subjective experience not adequately captured by a simple numeric scale; Theme 2: Conflict commonly exists between the patient's reported experience of pain and the clinician's observations and expectations of pain; Theme 3: Providers attempt to recalibrate the patient's reported experience to reflect their own understanding of pain; and Theme 4: Providers perceive that some patients may overreport their pain because they do not know how to standardize their subjective experience.

CONCLUSIONS

A persistent challenge to pain assessment and management is how clinicians reconcile a patient's subjective self-reported experience with their own clinical assessment and personal biases. Future work should explore these themes from the patient perspective.

What does "moderate pain" mean? Subgroups holding different conceptions of rating scales evaluate experimental pain differently

BACKGROUND

Pain ratings are almost ubiquitous in pain assessment, but their variability is high. Low correlations of continuous/numerical rating scales with categorical scales suggest that individuals associate different sensations with the same number on a scale, jeopardizing the interpretation of statistical results. We analysed individual conceptions of rating scales and whether these conceptions can be utilized in the analysis of ratings of experimental stimuli in pain-free healthy individuals and people with reoccurring/persistent pain.

METHODS

Using a free positioning task, healthy participants (N = 57) and people with reoccurring/persistent pain (N = 57) ad libitum positioned pain descriptors on lines representing intensity and un-/pleasantness scales. Furthermore, participants rated experimental thermal stimuli on visual analogue scales with the same end anchors. A latent class regression approach was used to detect subgroups with different response patterns in the free positioning task, indicating different conceptions of pain labels, and tested whether these subgroups differed in their ratings of experimental stimuli.

RESULTS

Subgroups representing different conceptions of pain labels could be described for the intensity and the un-/pleasantness scale with in part opposing response patterns in the free positioning task. Response patterns did not differ between people with and without pain, but in people with pain subgroups showed differential ratings of high intensity experimental stimuli.

CONCLUSIONS

Individuals' conceptions of pain labels differ. These conceptions can be quantified and utilized to improve the analysis of ratings of experimental stimuli. Identifying subgroups with different conceptions of pain descriptions could be used to improve predictions of responses to pain in clinical contexts.

SIGNIFICANCE

The present results provide a novel approach to incorporate individual conceptualizations of pain descriptors, which can induce large distortions in the analysis of pain ratings, in pain assessment. The approach can be used to achieve better pain estimates, representing individual conceptions of pain and achieving a better comparability between individuals but also between pain-free persons and patients with chronic pain. Particularly, in clinical settings this could improve quantification of perceived pain and the patient-clinician communication.

Ecological Momentary Assessment Methodology in Chronic Pain Research: A Systematic Review

Self-reported pain intensity assessments are central to chronic pain research. Ecological momentary assessment (EMA) methodologies are uniquely positioned to collect these data, and are indeed being used in the field. However, EMA protocols are complex, and many decisions are necessary in the design of EMA research studies. A systematic literature review identified 105 articles drawing from 62 quantitative EMA research projects examining pain intensity in adult chronic pain patients. Study characteristics were tabulated to summarize and describe the use of EMA, with an emphasis placed on various dimensions of decision-making involved in executing EMA methodologies. Most identified studies considered within-person relationships between pain and other variables, and a few examined interventions on chronic pain. There was a trend toward the use of smartphones as EMA data collection devices more recently, and completion rates were not reported in nearly one third of studies. Pain intensity items varied widely with respect to number of scale points, anchor labels, and length of reporting period; most used numeric rating scales. Recommendations are provided for reporting to improve reproducibility, comparability, and interpretation of results, and for opportunities to clarify the importance of design decisions.

PERSPECTIVE

Studies that use EMA methodologies to assess pain intensity are heterogeneous. Aspects of protocol design, including data input modality and pain item construction, have the potential to influence the data collected. Thorough reporting on design features and completion rates therefore facilitates reproducibility, comparability, and interpretation of study results.

Thermal QST Phenotypes Associated with Response to Lumbar Epidural Steroid Injections: A Pilot Study

Objective

Response to lumbar epidural steroid injection in lumbar radicular pain varies. The purpose of this study is to characterize the changes in quantitative sensory testing (QST) phenotypes of subjects and compare the QST characteristics in patients who do respond to treatment of radicular pain with a lumbar epidural steroid injection (ESI).

Design

Prospective, observational pilot study.

Setting

Outpatient pain center.

Methods

Twenty subjects with a lower extremity (LE) radicular pain who were scheduled to have an ESI were recruited. At the visit prior to and four weeks following an ESI, subjects underwent QST measurements of both the affected LE and the contralateral unaffected UE.

Results

Following an ESI, nine subjects reported a greater than 30% reduction in radicular pain and 11 reported a less than 30% reduction in radicular pain. Subjects who had less than 30% pain reduction response (nonresponders) to an ESI had increased pre-injection warm sensation threshold (37.30 °C, SD = 2.51 vs 40.39, SD = 3.36, P = 0.03) and heat pain threshold (47.22 °C, SD = 1.38, vs 48.83 °C, SD = 2.10, P = 0.04). Further, the nonresponders also showed increased pre-injection warm sensation threshold as measured in the difference of warm sensation detection threshold difference in the affected limb and the unaffected arm (2.68 °C, SD = 2.92 vs 5.67 °C, SD = 3.22, P  = 0.045). Other QST parameters were not affected.

Conclusions

The results show that the nonresponders to ESIs have increased detection threshold to heat pain and warm sensation, suggesting that a preexisting dysfunction in the C fibers in this group of subjects who can be detected by QST. Such altered QST characteristics may prognosticate the response to ESIs.

The Combination of IV and Perineural Dexamethasone Prolongs the Analgesic Duration of Intercostal Nerve Blocks Compared with IV Dexamethasone Alone

Objective

The use of multiple-level, single-injection intercostal nerve blocks for pain control following video-assisted thorascopic surgery (VATS) is limited by the analgesic duration of local anesthetics. This study examines whether the combination of perineural and intravenous (IV) dexamethasone will prolong the duration of intraoperatively placed intercostal nerve blocks following VATS compared with IV dexamethasone and a perineural saline placebo.

Design

Prospective, double-blind, randomized placebo-controlled trial.

Setting

Single level-1 academic trauma center.

Subjects

Forty patients undergoing a unilateral VATS under the care of a single surgeon.

Methods

Patients were randomly assigned to two groups and received an intercostal nerve block containing 1) 0.5% bupivacaine with epinephrine and 1 ml of 0.9% saline or 2) 0.5% bupivacaine with epinephrine and 1 ml of a 4 mg/ml dexamethasone solution. All patients received 8 mg of IV dexamethasone.

Results

Group 2 had lower NRS-11 scores at post-operative hours 8 (5.05, SD = 2.13 vs 3.50, SD = 2.50; p  = 0.04), 20 (4.30, SD = 2.96 vs 2.26, SD = 2.31; p  = 0.02), and 24 (4.53, SD = 1.95 vs 2.26, SD = 2.31; p  = 0.02). Equianalgesic opioid requirement was decreased in group 2 at 32 hours (5.78 mg, SD = 5.77 vs 1.67 mg, SD = 3.49; p  = 0.02). Group 2 also had greater FEV1 measured at 8, 12, 24, and 44 hours; greater FVC at 24 hours; greater PEF at 28 through 48 hours; and greater FEV1/FVC at 8 and 36 hours.

Conclusions

The combination of IV and perineural dexamethasone prolonged the duration of a single-injection bupivacaine intercostal nerve block as measured by NRS-11 compared with IV dexamethasone alone at 24 hours. Reduced NRS-11 at other times, reduced opioid requirements, and increased PFTs were observed in group 2.

Biopsychosocial factors associated with chronic low back pain disability in rural Nigeria: a population-based cross-sectional study

Introduction

Many people in Nigeria are living with disability due to chronic low back pain (CLBP), with the greatest burden accounted for by people living in rural Nigeria. However, factors associated with disability in rural Nigeria have not yet been established. We investigated the biomechanical and psychosocial predictors of CLBP disability in a rural Nigerian population.

Methods

A cross-sectional study of adults with non-specific CLBP recruited from rural communities in Enugu State, South-eastern Nigeria. Measures of self-reported and performance-based disability, pain intensity, anxiety and depression, coping strategies, social support, occupational biomechanical factors, illness perceptions and fear avoidance beliefs were collected by trained community health workers. We used univariate and multivariate analyses.

Results

200 individuals were recruited. Psychosocial factors were the most important factors associated with CLBP disability, and accounted for 62.5% and 49.1% of the variance in self-reported and performance-based disability, respectively. The significant predictors of self-reported disability were: illness perceptions (β=0.289; p<0.0005), pain intensity (β=0.230; p<0.0005), catastrophising (β=0.210; p=0.001), fear avoidance beliefs (β=0.198; p=0.001) and anxiety (β=0.154; p=0.023). The significant predictors of performance-based disability were: illness perceptions (β=0.366; p<0.0005), social support (β=0.290; p<0.0005), fear avoidance beliefs (β=0.189; p<0.01) and female gender (β=0.184; p<0.01). Illness concern was the most salient dimension of illness perceptions predicting self-reported and performance-based disability.

Conclusions

These results provide evidence which can be used to inform the development of interventions to reduce CLBP disability in rural Nigeria, and may have relevance in other rural African contexts.

Pain intensity rating training: results from an exploratory study of the ACTTION PROTECCT system

Clinical trial participants often require additional instruction to prevent idiosyncratic interpretations regarding completion of patient-reported outcomes. The Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION) public-private partnership developed a training system with specific, standardized guidance regarding daily average pain intensity ratings. A 3-week exploratory study among participants with low-back pain, osteoarthritis of the knee or hip, and painful diabetic peripheral neuropathy was conducted, randomly assigning participants to 1 of 3 groups: training with human pain assessment (T+); training with automated pain assessment (T); or no training with automated pain assessment (C). Although most measures of validity and reliability did not reveal significant differences between groups, some benefit was observed in discriminant validity, amount of missing data, and ranking order of least, worst, and average pain intensity ratings for participants in Group T+ compared with the other groups. Prediction of greater reliability in average pain intensity ratings in Group T+ compared with the other groups was not supported, which might indicate that training produces ratings that reflect the reality of temporal pain fluctuations. Results of this novel study suggest the need to test the training system in a prospective analgesic treatment trial.

Age Group Comparisons of TENS Response Among Individuals With Chronic Axial Low Back Pain

Chronic low back pain (CLBP) is a highly prevalent and disabling musculoskeletal pain condition among older adults. Transcutaneous electrical nerve stimulation (TENS) is commonly used to treat CLBP, however response to TENS in older adults compared with younger adults is untested. In a dose-response study stratified by age, 60 participants with axial CLBP (20 young, 20 middle-aged, 20 older) received four 20-minute sessions of high-frequency high-intensity TENS over a 2- to 3-week period in a laboratory-controlled setting. Experimental measures of pain sensitivity (mechanical pressure pain detection threshold) and central pain excitability (phasic heat temporal summation and heat aftersensations) were assessed before and after TENS. Episodic or immediate axial CLBP relief was assessed after TENS via measures of resting pain, movement-evoked-pain, and self-reported disability. Cumulative or prolonged axial CLBP relief was assessed by comparing daily pain reports across sessions. Independent of age, individuals experienced episodic increase in the pressure pain detection threshold and reduction in aftersensation after TENS application. Similarly, all groups, on average, experienced episodic axial CLBP relief via improved resting pain, movement-evoked pain, and disability report. Under this design, no cumulative effect was observed as daily pain did not improve for any age group across the 4 sessions. However, older adults received higher TENS amplitude across all sessions to achieve TENS responses similar to those in younger adults. These findings suggest that older adults experience similar episodic axial CLBP relief to that of younger individuals after high-frequency, high-intensity TENS when higher dose parameters are used.

PERSPECTIVE

This study examined age group differences in experimental and axial CLBP response to TENS, delivered under the current recommended parameters of strong, but tolerable amplitude. Older adults had comparable TENS response although at higher TENS amplitude than younger adults, which may have important mechanistic and clinical implications.

Pain rating schema: three distinct subgroups of individuals emerge when rating mild, moderate, and severe pain

Background

While the validity of pain assessment has been well documented, the underlying schema (ie, organized, preconceived ideas) of how individuals interpret numerical pain ratings is not well understood. This study’s objectives were to examine numerical pain intensity ratings, from (0 to 10 cm on the visual analog scale [VAS]) across multiple severities of commonly experienced acute pain conditions to determine whether the ratings differed between these pain conditions and/or between individuals.

Methods

A community sample (N=365, 66% female) rated their anticipated pain intensity (VAS) for threshold, mild, moderate, severe, and tolerance level, using several common pain conditions: headache, toothache, joint injury, delayed-onset muscle soreness, burns, and “general pain.”

Results

Cluster analysis revealed three subgroups of individuals, suggesting three types of underlying pain rating schema: 1) Low Rating subgroup (low VAS pain intensity ratings across all the pain severity categories); 2) Low/High Rating subgroup (low VAS pain intensity rating for mild, but high VAS pain intensity rating for severe pain); and 3) High Rating subgroup (high VAS pain intensity ratings across all the pain severity categories). Overall, differences between pain conditions were small: muscle soreness pain intensity was consistently rated lower than the other pain types across severities. The highest pain ratings varied between joint injury and general pain, depending on severity level. No effects of sex or current experience of pain were noted.

Conclusion

The results indicate that: 1) three distinct pain schemas were present in this community-based sample, indicating significant variation in how pain scales are utilized and/or interpreted between clusters of individuals; 2) pain ratings vary by condition, but these differences are minor; and 3) pain rating schemas are not significantly different between males and females or between individuals with and without current pain.

Is it a (fe)male pain? Portuguese nurses' and laypeople's gendered representations of common pains

BACKGROUND

Although many studies have explored gender role expectations of pain behaviours in different cultures, only a few authors have tried to explore whether certain pains are more associated with the typical man or woman. Hence, this study aimed at exploring, among Portuguese laypeople and nurses, patterns of common pains more strongly associated with the typical man or woman, and their relationship with health-care training and personal pain experiences.

METHODS

A total of 68 nurses (76% women) and 55 laypeople (62% women) were asked to identify, through free association, the most frequent common pains that people in general associate with the typical man and woman, respectively, and also to report their personal past pain experiences. A content analysis was used to categorize and quantify participants' responses. A multiple correspondence analysis was performed to identify gendered patterns of common pains, followed by a cluster analysis to classify participants according to their endorsed patterns.

RESULTS

Findings showed that while 'back and musculoskeletal pains' was the only pattern associated with the typical man, more differentiated patterns of pains were associated with the typical woman, namely (1) headaches; (2) abdominal, back and musculoskeletal pains; and (3) pains due to hormonal cycles, labour/puerperium and from the urinary/reproductive system. These representations were shared by laypeople and nurses and were only significantly associated with personal experiences of pains from the urinary/reproductive system.

CONCLUSIONS

This study identified different gendered patterns of common pains, which may have important implications for (wo)men's pain experiences and how these are interpreted by others.

Do past pain events systematically impact pain ratings of healthy subjects or fibromyalgia patients?

We previously reported that 3 different electronic visual analogue and numerical pain scales are useful in providing refined capacity to discriminate discrete levels of pain intensity. Using the same subjects and scales, we now investigated whether pain scaling is influenced by past pain events and by recalled memories of these events in the rating of pain. Normal control subjects (NC: 19 male, 30 female) and female fibromyalgia (FM) (n = 17) patients received 5-second suprathreshold heat stimuli (45-49 degrees C) to both forearms. The participants rated these experimental heat stimuli using the previously described electronic pain scales. Subsequently, they were asked to report whether they used any prior pain experiences during the process of rating their pain. Out of 49 NC, only 6 females (12.2%) and 7 males (14.3%), and out of 17 FM patients, only 3 females (17.6%) stated that they had used past pain experiences during scaling. Notably, pain ratings of experimental heat stimuli did not statistically differ between subjects who used past pain experiences during scaling as compared to those who did not. Furthermore, ratings of their most severe past pains were not significantly correlated with ratings of experimental pain stimuli. These results do not provide support for the strong assertion that pain rating scales are elastic, ie, being used differently depending on the severity of past pain events such as childbirth.

PERSPECTIVE

Less than 25% of subjects used memories of past pain events during pain scaling. In addition, if they were used, these pain memories did not influence pain scaling with electronic eVAS and eNUM scales. Thus, use of these scales allows reliable comparisons of experimental and clinical pain ratings within and between subjects.

Sex differences in prior pain experience

Sex differences in clinical and experimental pain experiences are well documented. However, there has been little work investigating men's and women's experiences with common painful events. This study examined sex differences in the nature and intensity of common pain experiences. Participants (102 women and 85 men) completed the Prior Pain Experience Questionnaire, which is a 79-item assessment of an individual's pain experience, recalled pain ratings, and imagined pain ratings. Analyses of variance were conducted to assess for sex differences in overall pain experience and pain ratings. Men and women did not have significant differences in the overall number of reported pain experiences or in the overall mean pain rating of those experiences. However, they differed in specific pain events experienced (eg, men experienced concussions more than women) and pain ratings (eg, women rated minor surgery as significantly more painful than men). Individuals who imagined pain events tended to rate them as equally or more painful than individuals who experienced those pain events.

PERSPECTIVE

Results of this study demonstrate that men and women have varying types of pain experiences without evidence that the overall pain experience differs between sexes. It was also found that imagined pain ratings are often worse than experienced pain ratings, lending support for the tendency of individuals to catastrophize.