Classifying chronic pain using multidimensional pain-agnostic symptom assessments and clustering analysis

PROGRESS: A Patient-centered Engagement Infrastructure and Multi-level Approach to Enrich Diversity, Equity, and Inclusion in a National Randomized Online Behavioral Pain Treatment Study

Twenty percent of individuals experience chronic pain worldwide posing significant challenges to those living with it. Pain research is crucial for developing and characterizing effective strategies to reduce the burden of chronic pain. Traditional research approaches often yield homogeneous study samples that poorly generalize and have unknown applicability across diverse patient populations. The Pain Relief with Online Groups that Empower Skills-based Symptom Reduction (PROGRESS) study aims to address disparities in pain research engagement and patient outcomes through the intentional inclusion of people with varied backgrounds and experiences of pain, and through a multilevel design informed by diverse stakeholder recommendations. The composition of three advisory boards (Patient Engagement and Diversity Board, Local Patient Advisory Board, and the National Patient Advisory Panel) prioritized diversity in patient/expert advisor background, geographic location, race, and ethnicity. Our engagement approach aligns with the Foundational Expectations for Partnerships in Research by Patient-Centered Outcomes Research Institute (PCORI), which emphasizes diverse representation, early and ongoing engagement, dedicated funds for advisor compensation, collaborative decision making, meaningful participation, and continuous assessment. The first 24 months of study advisor engagement has yielded multiple recruitment strategies resulting in a study population enriched with a breadth of identities within PROGRESS (e.g., inclusive patient-facing materials). Lessons learned underscore the importance of investing time in building patient and stakeholder relationships, trust, and embracing diverse viewpoints amongst the study team. PROGRESS demonstrates the potential of diverse patient-centered engagement to support evidence-based outcomes and practices that are more inclusive, equitable, and representative of the broader population. PERSPECTIVE: The PROGRESS study demonstrates how diverse patient engagement and inclusive advisory boards enhance research outcomes. By aligning with PCORI standards and employing innovative recruitment strategies, it highlights the vital role of stakeholder relationships and diverse perspectives. Key lessons learned emphasize adaptive strategies and continuous feedback for advancing equitable pain research.

Is There an Association Between Lateralization of Chronic Pain in the Body and Depression?

Depression commonly co-occurs with chronic pain and can worsen pain outcomes. Recent theoretical work has hypothesized that pain localized to the left hemibody is a risk factor for worse depression due to overlap in underlying neural substrates. This hypothesis has not been tested a priori. Using a large sample of treatment-seeking adults with mixed-etiology chronic pain (N = 1,185), our cross-sectional study tested whether patients with left-sided pain endorse worse depressive symptoms. We also examined differences in other pain-related functioning measures. We tested 4 comparisons based on painful body areas using the CHOIR body map: 1) only left-sided (OL) versus any right-sided pain; 2) only right-sided (OR) versus any left-sided pain; 3) OL versus OR versus bilateral pain; and 4) more left-sided versus more right-sided versus equal-sided pain. Analysis of variance models showed OL pain was not associated with worse depression (F = 5.50, P = .019). Any left-sided pain was associated with worse depression, though the effect was small (F = 8.58, P = .003, Cohens d = .29). Bilateral pain was associated with worse depression (F = 8.05, P < .001, Cohens d = .24-.33). Regardless of pain location, more body areas endorsed was associated with greater depression. Although a more rigorous assessment of pain laterality is needed, our findings do not support the hypothesis that left-lateralized pain is associated with worse depression. PERSPECTIVE: Pain lateralized to the left side of the body has been hypothesized as a risk factor for worse depression in chronic pain, despite never being tested in a large, real-world sample of patients with chronic pain. Findings showed that more widespread pain, not pain laterality, was associated with worse depression.

Nociplastic Pain: A Critical Paradigm for Multidisciplinary Recognition and Management

Our understanding of chronic pain has evolved significantly, shifting from a focus on peripheral damage to recognizing the central mechanisms underlying pain perception. This perspective article explores the concept of nociplastic pain, a term introduced by the International Association for the Study of Pain (IASP) in 2017, which describes pain arising from altered pain modulation within the central nervous system, without clear evidence of tissue damage or inflammation. The historical progression from fibrositis to fibromyalgia, and now to nociplastic pain, underscores the complexity of chronic pain syndromes and the need for a multidisciplinary approach to management. Nociplastic pain is characterized by central sensitization, leading to heightened pain sensitivity and often accompanied by comorbidities such as fatigue, sleep disturbances, and cognitive difficulties. Advances in neuroimaging have revealed altered connectivity within key brain networks, such as the default mode and salience networks, in patients with nociplastic pain, providing insights into the neural underpinnings of this condition. The article also addresses controversies surrounding the role of small fiber neuropathy and autonomic dysfunction in nociplastic pain, highlighting the ongoing debates in the field. The practical importance of recognizing nociplastic pain across various medical disciplines-including primary care, orthopedics, neurology, psychiatry, and rheumatology-is emphasized, with recommendations for integrating this knowledge into clinical practice. Emerging therapies, such as neurofeedback, hyperbaric oxygen therapy, and neuromodulation, offer new avenues for treatment, particularly for patients who do not respond to conventional approaches. The article calls for continued research into the mechanisms of nociplastic pain, the development of reliable diagnostic tools, and the exploration of novel therapeutic strategies to improve patient outcomes. The recognition and management of nociplastic pain are crucial for advancing the care of patients with chronic pain, necessitating interdisciplinary collaboration and a patient-centered approach.

Expectation of pain and relief: A dynamical model of the neural basis for pain-trauma co-morbidity

Posttraumatic Stress Disorder (PTSD) is highly co-morbid with chronic pain conditions. When present, PTSD significantly worsens chronic pain outcomes. Likewise, pain contributes to a more severe PTSD as evidenced by greater disability, more frequent use of harmful opioid analgesics and increased pain severity. The biomechanism behind this comorbidity is incompletely understood, however recent work strongly supports the widely-accepted role of expectation, in the entanglement of chronic pain and trauma symptoms. This work has shown that those with trauma have a maladaptive brain response while expecting stress and pain, whereas those with chronic pain may have a notable impairment in brain response while expecting pain relief. This dynamical expectation model of the interaction between neural systems underlying expectation of pain onset (traumatic stress) and pain offset (chronic pain) is biologically viable and may provide a biomechanistic insight into pain-trauma comorbidity. These predictive mechanisms work through interoceptive pathways in the brain critically the insula cortex. Here we highlight how the neural expectation-related mechanisms augment the existing models of pain and trauma to better understand the dynamics of pain and trauma comorbidity. These ideas will point to targeted complementary clinical approaches, based on mechanistically separable neural biophenotypes for the entanglement of chronic pain and trauma symptoms.

Characterizing phenotypes and clinical and health utilization associations of young people with chronic pain: latent class analysis using the electronic Persistent Pain Outcomes Collaboration database

ABSTRACT

Using the Australiasian electronic Persistent Pain Outcomes Collaboration, a binational pain registry collecting standardized clinical data from paediatric ePPOC (PaedsePPOC) and adult pain services (AdultePPOC), we explored and characterized nationally representative chronic pain phenotypes and associations with clinical and sociodemographic factors, health care utilization, and medicine use of young people. Young people ≥15.0 and <25.0 years captured in PaedePPOC and AdultePPOC Australian data registry were included. Data from 68 adult and 12 paediatric pain services for a 5-year period January 2018 to December 2022 (first episode, including treatment information) were analysed. Unsupervised latent class analysis was applied to explore the existence of distinct pain phenotypes, with separate models for both services. A 3-phenotype model was selected from both paediatric and adult ePPOC data, with 693 and 3518 young people included, respectively (at least one valid indicator variable). Indicator variables for paediatric models were as follows: pain severity, functional disability (quasisurrogate "pain interference"), pain count, pain duration, pain-related worry (quasisurrogate "catastrophizing"), and emotional functioning; and, for adult models: pain severity, pain interference, pain catastrophizing, emotional functioning, and pain self-efficacy. From both services, 3 similar phenotypes emerged ("low," "moderate," "high"), characterized by an increasing symptom-severity gradient in multidimensional pain-related variables, showing meaningful differences across clinical and sociodemographic factors, health service utilization, and medicines use. Derived phenotypes point to the need for novel care models that differentially respond to the needs of distinct groups of young people, providing timely, targeted, age-appropriate care. To effectively scale such care, digital technologies can be leveraged to augment phenotype-informed clinical care.

The Impact of Non-Pain Factors on Pain Interference Among U.S. Service Members and Veterans with Symptoms of Mild Traumatic Brain Injury

U.S. Service members and Veterans (SM/V) experience elevated rates of traumatic brain injury (TBI), chronic pain, and other non-pain symptoms. However, the role of non-pain factors on pain interference levels remains unclear among SM/Vs, particularly those with a history of TBI. The primary objective of this study was to identify factors that differentiate high/low pain interference, given equivalent pain intensity among U.S. SM/V participating in the ongoing Long-term Impact of Military-relevant Brain Injury Consortium-Chronic Effects of Neurotrauma Consortium (LIMBIC-CENC) national multi-center prospective longitudinal observational study. An explainable machine learning was used to identify key predictors of pain interference conditioned on equivalent pain intensity. The final sample consisted of n = 1,577 SM/Vs who were predominantly male (87%), and 83.6% had a history of mild TBI(s) (mTBI), while 16.4% were TBI negative controls. The sample was categorized according to pain interference level (Low: 19.9%, Moderate: 52.5%, and High: 27.6%). Both pain intensity scores and pain interference scores increased with the number of mTBIs (p < 0.001), and there was evidence of a dose response between the number of injuries and pain scores. Machine learning models identified fatigue and anxiety as the most important predictors of pain interference, whereas emotional control was protective. Partial dependence plots identified that marginal effects of fatigue and anxiety were associated with pain interference (p < 0.001), but the marginal effect of mTBI was not significant in models considering all variables (p > 0.05). Non-pain factors are associated with functional limitations and disability experience among SM/V with an mTBI history. The functional effects of pain may be mediated through multiple other factors. Pain is a multi-dimensional experience that may benefit most from holistic treatment approaches that target comorbidities and build supports that promote recovery.

Perceived Injustice and Anger in Fibromyalgia With and Without Comorbid Mental Health Conditions: A Hebrew Validation of the Injustice Experience Questionnaire

OBJECTIVES

Perceived injustice (PI), assessed by the Injustice Experience Questionnaire (IEQ), is an important trigger of anger. Both PI and anger are associated with adverse chronic pain outcomes, and with comorbid mental health severity. We aimed examined the roles of PI and anger in mediating pain across Fibromyalgia patients, with and without comorbid anxiety/depression (FM+A/D, FM-A/D, respectively), as well as rheumatoid arthritis (RA), and pain-free controls (PFC). We hypothesized the highest levels of PI, anger, and pain in FM+A/D patients, followed by FM-A/D, RA, and PFC, thus also validating a Hebrew version of the IEQ.

METHODS

We translated the IEQ using the forward-backward method and collected data online. Based on self-reported anxiety/depression, the sample comprised 66 FM+A/D patients, 64 FM-A/D, 34 RA, and 32 PFCs. Assessments included the IEQ, state and trait anger, pain intensity, anxiety, depression, and pain catastrophizing. The structure and reliability of the Hebrew IEQ were examined using factor analysis and Cronbach alpha. Bootstrapped-based modeling was used to test the roles of state and trait anger in mediating and moderating the relationship between PI and pain intensity.

RESULTS

We confirmed a one-factor structure of the IEQ, with excellent reliability. FM+A/D patients demonstrated the highest scores in all measures. Within this group, trait anger moderated the mediating effect of state anger in the relationship between PI and pain intensity.

DISCUSSION

Our findings validate a Hebrew IEQ and highlight the importance of PI and state and trait anger in the differential manifestation of mental health comorbidity in FM.

Establishing the interpretability and utility of the 4-item BriefPCS

To reduce the patient burden associated with completing the 13-item Pain Catastrophizing Scale (PCS), the 4-item "BriefPCS" was developed. To date, no crosswalk has been developed that associates scores on the BriefPCS with PCS scores. Further, no study has compared the use of BriefPCS and PCS scores in a randomized clinical trial (RCT). We aimed to: (1) establish the interpretability of BriefPCS scores in reference to PCS scores, (2) compare the concurrent validity between the BriefPCS and PCS, and (3) asssess the use of BriefPCS in an RCT. First, we conducted equipercentile linking, created a crosswalk that associated scores of BriefPCS with PCS, and calculated differences between PCS and crosswalked PCS scores. Secondly, we compared Bootstrap correlation coefficients between PCS and self-reported measures of other domains. Lastly, we compared results from an RCT using BriefPCS scores versus PCS scores. Findings indicated that the correlation coefficient estimates with the BriefPCS and PCS scores were not significantly different. BriefPCS and PCS scores had similar ability to detect treatment-related changes. The BriefPCS scores validly, reliably, and accurately distinguish levels of pain catastrophizing. Additionally, the BriefPCS scores are sensitive to changes after behavioral interventions, with less respondent burden compared to the PCS scores.

Personalized pain management: Is it time for process-based therapy for particular people with chronic pain?

BACKGROUND AND OBJECTIVE

Psychological treatments for chronic pain have helped many people around the world. They are among the most researched and best evidenced treatments a person can receive when they have persistent, disabling and distressing pain. At the same time, improvements in the effectiveness of these treatments appear to be at a standstill. This may be due to an inherent lack of generalizability from aggregated group data to the individual, limited utility of our current schemes for categorizing people with pain conditions, faced with their inherent heterogeneity, our relatively coarse categories of treatment types and focus on treatment packages rather than individual methods, and our current failures to find adequate predictors of outcome, or to assign people their best-suited treatment methods, based on group data. In this review, it is argued that the development and examination of truly personalized treatment is a next logical step to create progress and improve the results people achieve.

METHODS

Key research studies pertaining to psychological treatments, treatment outcome, heterogeneity in chronic pain, prediction of treatment outcome, subtyping and treatment tailoring are reviewed.

RESULTS AND CONCLUSION

It is suggested that development of future treatments for chronic pain ought to incorporate an idiographic, process-based approach, focused on evidence-based mechanisms of change, individually and dynamically addressed, based on contextually sensitive ongoing assessment. Knowledge and practical solutions needed to make process-based therapy for chronic pain happen are discussed.

SIGNIFICANCE

Psychological approaches to chronic pain have been highly successful in the past but improvement in the effectiveness of these over time is slow to nonexistent. It is argued here that this has happened due to a failure to adequately consider the individual. Future psychological treatments for chronic pain ought to incorporate an idiographic, process-based approach, focused on evidence-based mechanisms of change, individually and dynamically addressed, grounded in ongoing contextually sensitive assessment.

A Longitudinal Investigation of the Impact of COVID-19 on Patients With Chronic Pain

The COVID-19 pandemic prompted unexpected changes in the healthcare system. This current longitudinal study had 2 aims: 1) describe the trajectory of pandemic-associated stressors and patient-reported health outcomes among patients receiving treatment at a tertiary pain clinic over 2 years (May 2020 to June 2022); and 2) identify vulnerable subgroups. We assessed changes in pandemic-associated stressors and patient-reported health outcome measures. The study sample included 1270 adult patients who were predominantly female (74.6%), White (66.2%), non-Hispanic (80.6%), married (66.1%), not on disability (71.2%), college-educated (59.45%), and not currently working (57.9%). We conducted linear mixed effect modeling to examine the main effect of time with controlling for a random intercept. Findings revealed a significant main effect of time for all pandemic-associated stressors except financial impact. Over time, patients reported increased proximity to COVID-19, but decreased pandemic-associated stressors. A significant improvement was also observed in pain intensity, pain catastrophizing, and PROMIS-pain interference, sleep, anxiety, anger, and depression scores. Demographic-based subgroup analyses for pandemic-associated stressors revealed that younger adults, Hispanics, Asians, and patients receiving disability compensation were vulnerable groups either during the initial visit or follow-up visits. We observed additional differential pandemic effects between groups based on participant sex, education level, and working status. In conclusion, despite unanticipated changes in pain care services during the pandemic, patients receiving pain treatments adjusted to pandemic-related stressors and improved their health status over time. As the current study observed differential pandemic impacts on patient subgroups, future studies should investigate and address the unmet needs of vulnerable subgroups. PERSPECTIVE: Over a 2-year timeframe, the pandemic did not adversely influence physical and mental health among treatment-seeking patients with chronic pain. Patients reported small but significant improvements across indices of physical and psychosocial health. Differential impacts emerged among groups based on ethnicity, age, disability status, gender, education level, and working status.

Pragmatic Comparative Effectiveness Trials and Learning Health Systems in Pain Medicine: Opportunities and Challenges

Large randomized clinical trials or aggregates of clinical trials represent the highest levels of clinical evidence because they minimize different sources of confounding and bias. The current review provides an in-depth discussion of the challenges faced and methods we can use to overcome these obstacles to tailor novel designs of pragmatic effectiveness trials to pain medicine. The authors describe their experiences with an open-source learning health system to collect high-quality evidence and conduct pragmatic clinical trials within a busy academic pain center.

Unsupervised learning for prognostic validity in patients with chronic pain in transdisciplinary pain care

Chronic pain is not a singular disorder and presents in various forms and phenotypes. Here we show data from a cohort of patients seeking treatment in a transdisciplinary pain clinic. Patients completed a multidimensional patient-reported battery as part of routine initial evaluation at baseline and at each of the four subsequent visits over 1-year follow-up (0, 1, 3, 6, 12 months). The goal of this work was to use unsupervised modeling approach to identify whether patients with chronic pain undergoing transdisciplinary intensive rehabilitation treatment: (1) can be derived based upon self-reported outcome measures at baseline (or before treatment initiation), (2) are clinically validated based on their clinical diagnosis and medication use, and (3) differ in treatment trajectories over 1 year of transdisciplinary treatment. We applied unsupervised clustering on baseline outcomes using nine patient-reported symptoms and examined treatment trajectories. The three-cluster solution was internally validated. Psychiatric diagnosis, chronic back pain-related disability and symptoms severity determined cluster assignment and treatment prognosis. Conversely, clinical pain severity had lesser effect. Furthermore, clusters showed stability over time despite symptoms improvement. The accurate and meaningful subgrouping of the underlying chronic pain phenotypes would greatly enhance treatment and provide personalized and effective pain management.

Real-world data and evidence in pain research: a qualitative systematic review of methods in current practice

The use of routinely collected health data (real-world data, RWD) to generate real-world evidence (RWE) for research purposes is a growing field. Computerized search methods, large electronic databases, and the development of novel statistical methods allow for valid analysis of data outside its primary clinical purpose. Here, we systematically reviewed the methodology used for RWE studies in pain research. We searched 3 databases (PubMed, EMBASE, and Web of Science) for studies using retrospective data sources comparing multiple groups or treatments. The protocol was registered under the DOI:10.17605/OSF.IO/KGVRM. A total of 65 studies were included. Of those, only 4 compared pharmacological interventions, whereas 49 investigated differences in surgical procedures, with the remaining studying alternative or psychological interventions or epidemiological factors. Most 39 studies reported significant results in their primary comparison, and an additional 12 reported comparable effectiveness. Fifty-eight studies used propensity scores to account for group differences, 38 of them using 1:1 case:control matching. Only 17 of 65 studies provided sensitivity analyses to show robustness of their findings, and only 4 studies provided links to publicly accessible protocols. RWE is a relevant construct that can provide evidence complementary to randomized controlled trials (RCTs), especially in scenarios where RCTs are difficult to conduct. The high proportion of studies reporting significant differences between groups or comparable effectiveness could imply a relevant degree of publication bias. RWD provides a potentially important resource to expand high-quality evidence beyond clinical trials, but rigorous quality standards need to be set to maximize the validity of RWE studies.