Quantitative sensory testing and pain-evoked cytokine reactivity: comparison of patients with sickle cell disease to healthy matched controls

A randomized controlled study of auricular point acupressure to manage chemotherapy-induced neuropathy: Study protocol

OBJECTIVE

Chemotherapy-induced neuropathy (CIN) significantly impacts cancer patients, leading to functional disability, diminished quality of life, and increased healthcare costs amid the ongoing opioid crisis. Auricular point acupressure (APA), a non-invasive and non-pharmacological alternative, has shown potential for alleviating the pain, numbness, and tingling associated with CIN. This study aims to assess the efficacy of APA for CIN symptoms and physical function and to examine the mechanisms underlying APA's effects on CIN.

METHODS

This is a three-arm randomized controlled clinical trial protocol. Patients aged 18 and older who are experiencing CIN are randomly assigned to one of the three groups: an APA group (in-person APA; mAPA), a sham control group (virtual APA; vAPA), and a wait-list usual care control group (UC). During the four-week program, participants in the mAPA receive an in-person APA treatment and training; the sham control participants (vAPA) receive a self-guided smartphone APA application with APA demonstration videos; and the UC participants will continue with the usual care and be re-randomized into one of the APA groups. The primary outcomes are changes in CIN symptoms and physical function. Secondary outcomes include evaluating pain sensory thresholds, motor and cognitive functioning, inflammatory signaling, brain connectivity, opioid use, and quality of life. The outcomes are measured at baseline, program completion (4 weeks), and at monthly follow-up for 3 months post-intervention.

DISCUSSION

This study will provide evidence supporting the potential viability of APA as an intervention for CIN.

TRIAL REGISTRATION

ClinicalTrials.gov, ID NCT04920097 registered on 3 June 2021.

Genetic contributions to pain modulation in sickle cell: A focus on single nucleotide polymorphisms

Background

Despite recent advances in our knowledge of genetic contributions to the highly variable sickle cell disease (SCD) phenotype, our understanding of genetic factors associated with pain sensitivity in SCD remains limited. Previous studies investigated specific variants in single candidate genes and their association with SCD pain variability. The primary aim of the current study was to expand the genes and polymorphisms tested to discover new risk genes (polymorphisms) associated with central sensitization for individuals with SCD.

Methods

Adults with sickle cell disease (n = 59, Mage = 36.8 ± 11.5, 65.8 % female) underwent quantitative sensory testing to examine central sensitization and general pain sensitivity. Participants reported average crisis and non-crisis pain intensities weekly using a 0-100 scale, and provided salivary samples for genotyping. The Hardy-Weinberg equilibrium was verified for controls, and allele distributions were tested with chi-square and odds ratio tests. The Benjamini-Hochberg procedure was used to control for false discovery rate. Regression analyses and Wilcoxon tests were used to test associations for normally distributed and skewed data, respectively.

Results

Central sensitization and general pain sensitivity were not associated with hemoglobin genotype (Ps > 0.05). Of 4145 SNPs tested, following false discovery rate adjustments, 11 SNPs (rs11575839, rs12185625, rs12289836, rs1493383, rs2233976, rs3131787, rs3739693, rs4292454, rs4364, rs4678, rs6773307) were significantly associated with central sensitization, and one SNP (rs7778077) was significantly associated with average weekly non-crisis pain. No SNPs were associated with general pain sensitivity.

Conclusions

These findings provide insights into genetic variants association with average non-crisis pain and central sensitization for individuals with SCD, and may provide support for genetic predictors of heightened pain experience within SCD.

Altered pain processing and sensitization in sickle cell disease: a scoping review of quantitative sensory testing findings

OBJECTIVES

Over 50% of adults living with sickle cell disease (SCD) have chronic pain, but the underlying mechanisms of chronic pain in this population remain unclear. Quantitative sensory testing is an important measurement tool for understanding pain and sensory processing. This scoping review summarizes quantitative sensory testing methodologies used in sickle cell studies and the evidence for central sensitization in this population.

METHODS

We conducted a systematic search of PubMed, Embase, and CINAHL to identify studies using quantitative sensory testing in individuals living with sickle cell disease. Search strategies were based on variations of the terms "sickle cell disease," and "quantitative sensory testing." Eligible studies were observational or experimental studies in human participants living with SCD that reported findings and detailed methodology for at least 1 quantitative sensory testing modality.

RESULTS

Our search yielded a total of 274 records; 27 of which are included in this scoping review. Of the 27 studies, 17 were original studies (with combined total of 516 adult and 298 pediatric participants), and 10 were secondary or subgroup analyses of these prior studies. Significant variation existed in quantitative sensory testing methodologies across studies, including testing locations, type and intensity of stimuli, and interpretation of findings. Of the identified studies, 22% (2/9 studies) reported sensory abnormalities in mechanical sensitivity and thresholds, 22% (2/9 studies) reported abnormal pressure pain thresholds, 46% (6/13 studies) reported sensory abnormalities in thermal pain thresholds and tolerance (cold and warm), and 50% (2/4 studies) reported abnormalities in temporal summation.

CONCLUSION

Future studies should use standardized quantitative sensory testing protocols with consistent and operationalized definitions of sensitization to provide clear insight about pain processing and central sensitization in sickle cell disease.

Differential clinical characteristics across traditional Chinese medicine (TCM) Syndromes in patients with sickle cell disease

Background

Pain is a common, debilitating, and poorly understood complication of sickle cell disease (SCD). The need for clinical pain management of SCD is largely unmet and relies on opioids as the main therapeutic option, which leads to a decreased quality of life (QoL). According to the literature, acupuncture has shown certain therapeutic effects for pain management in SCD. However, these clinical studies lack the guidance of Traditional Chinese Medicine (TCM) Syndrome Differentiation principles for treatment.

Aim

To characterize differences in clinical presentation amongst TCM diagnosed Syndromes in SCD patients.

Method

Fifty-two patients with SCD and 28 age- and sex-matched healthy controls (HCs) were enrolled in an ongoing trial of acupuncture. Each participant completed a series of questionnaires on pain, physical function, fatigue, sleep, anxiety, depression and QoL and underwent cold- and pressure-based quantitative sensory testing at baseline. Data on prescription opioid use over the 12 months prior to study enrollment was used to calculate mean daily morphine milligram equivalents (MME). Differences among the three TCM Syndromes were analyzed by one-way ANOVA followed by Tukey post hoc testing. Two-sample t-tests were used to compare SCD and HC groups.

Results

TCM diagnosis criteria classified SCD patients into one of three TCM Syndromes: (a) Equal; (b) Deficiency; and (c) Stagnation. The Stagnation group exhibited higher pain interference, physical dysfunction, nociplastic pain, fatigue, anxiety, depression, MME consumption and lower sleep quality and QoL compared to the Equal group. Few differences were observed between HCs and the Equal SCD group across outcomes. Deficiency and Stagnation groups were differentiated with observed- and patient-reported clinical manifestations.

Conclusion

These findings suggest that TCM diagnosed Syndromes in SCD can be differentially characterized using validated objective and patient-reported outcomes. Because characteristics of pain and co-morbidities in each SCD patient are unique, targeting specific TCM "Syndromes" may facilitate treatment effectiveness with a Syndrome-based personalized treatment plan that conforms to TCM principles. These findings lay the foundation for the development of tailored acupuncture interventions based on TCM Syndromes for managing pain in SCD. Larger samples are required to further refine and validate TCM diagnostic criteria for SCD.

Physical, functional and personal variables affecting shoulder complaints in healthcare workers

BACKGROUND

Work-related shoulder disorders adversely affect the quality of life and lead to increased costs related to decreased productivity and injury treatment. Therefore, understanding the relationship between strength, upper extremity function and work ability contributes to the development of interventions aimed to improve the well-being of healthcare workers.

OBJECTIVE

Correlate shoulder abduction and handgrip strength with upper extremity function and work ability in healthcare workers with shoulder complaints.

METHODS

67 workers with shoulder pain in the last year were assessed by Disability of Arm, Shoulder and Hand (QuickDASH), Work Ability Index (WAI), isokinetic shoulder strength and isometric handgrip strength dynamometers. Data were analysed with Spearman's Correlation Coefficient (ρ= 0.05), SPSS 20.0®.

RESULTS

52% males, mean age 48.4 years, 42% physically active, most administrative and general services workers. Low correlation between handgrip strength and QuickDASH (r=-0.359; p = 0.004); low correlation between handgrip strength and WAI (r = 0.359; p = 0.003) and between shoulder abduction strength and the QuickDASH (r = -0.267; p = 0.049); no significant correlation between shoulder abduction strength and WAI (r = 0.001; p = 0.997).

CONCLUSIONS

Handgrip and shoulder abduction strength were inversely associated with upper extremity dysfunction. Shoulder abduction strength was associated with work ability. The inclusion of strength assessment in workers is important to guide strategies to prevent musculoskeletal disorders.

Cold exposure induces vaso-occlusion and pain in sickle mice that depend on complement activation

Vaso-occlusive pain episodes (VOE) cause severe pain in patients with sickle cell disease (SCD). Vaso-occlusive events promote ischemia/reperfusion pathobiology that activates complement. We hypothesized that complement activation is linked to VOE. We used cold to induce VOE in the Townes sickle homozygous for hemoglobin S (HbSS) mouse model and complement inhibitors to determine whether anaphylatoxin C5a mediates VOE. We used a dorsal skinfold chamber to measure microvascular stasis (vaso-occlusion) and von Frey filaments applied to the plantar surface of the hind paw to assess mechanical hyperalgesia in HbSS and control Townes mice homozygous for hemoglobin A (HbAA) mice after cold exposure at 10°C/50°F for 1 hour. Cold exposure induced more vaso-occlusion in nonhyperalgesic HbSS mice (33%) than in HbAA mice (11%) or HbSS mice left at room temperature (1%). Cold exposure also produced mechanical hyperalgesia as measured by paw withdrawal threshold in HbSS mice compared with that in HbAA mice or HbSS mice left at room temperature. Vaso-occlusion and hyperalgesia were associated with an increase in complement activation fragments Bb and C5a in plasma of HbSS mice after cold exposure. This was accompanied by an increase in proinflammatory NF-κB activation and VCAM-1 and ICAM-1 expression in the liver. Pretreatment of nonhyperalgesic HbSS mice before cold exposure with anti-C5 or anti-C5aR monoclonal antibodies (mAbs) decreased vaso-occlusion, mechanical hyperalgesia, complement activation, and liver inflammatory markers compared with pretreatment with control mAb. Anti-C5 or -C5aR mAb infusion also abrogated mechanical hyperalgesia in HbSS mice with ongoing hyperalgesia at baseline. These findings suggest that C5a promotes vaso-occlusion, pain, and inflammation during VOE and may play a role in chronic pain.

Differential clinical characteristics across traditional Chinese medicine (TCM) syndromes in patients with sickle cell disease

Background

Pain is a common, debilitating, and poorly understood complication of sickle cell disease (SCD). The need for clinical pain management of SCD is largely unmet and relies on opioids as the main therapeutic option, which leads to a decreased quality of life (QoL). According to the literature, acupuncture has shown certain therapeutic effects for pain management in SCD. However, these clinical studies lack the guidance of Traditional Chinese Medicine (TCM) Syndrome Differentiation principles for treatment.

Aim

To characterize differences in clinical presentation amongst TCM-diagnosed syndromes in SCD patients.

Method

52 patients with SCD and 28 age- and sex-matched healthy controls (HCs) were enrolled in an ongoing trial of acupuncture. Each participant completed a series of questionnaires on pain, physical function, fatigue, sleep, anxiety, depression, and QoL and underwent cold- and pressure-based quantitative sensory testing at baseline. Data on prescription opioid use over the 12 months prior to study enrollment was used to calculate mean daily morphine milligram equivalents (MME). Differences among the three TCM syndromes were analyzed by one-way ANOVA followed by Tukey post hoc testing. Two-sample t-tests were used to compare SCD and HC groups.

Results

TCM diagnosis criteria classified SCD patients into one of three TCM syndromes: a) Equal; b) Deficiency; and c) Stagnation. The Stagnation group exhibited higher pain interference, physical dysfunction, nociplastic pain, fatigue, anxiety, depression, MME consumption, and lower sleep quality and QoL compared to the Equal group. Few differences were observed between HCs and the Equal SCD group across outcomes. Deficiency and Stagnation groups were differentiated with observed- and patient-reported clinical manifestations.

Conclusion

These findings suggest that TCM-diagnosed syndromes in SCD can be differentially characterized using validated objective and patient-reported outcomes. Because characteristics of pain and co-morbidities in each SCD patient are unique, targeting specific TCM "syndromes" may facilitate treatment effectiveness with a syndrome-based personalized treatment plan that conforms to TCM principles. These findings lay the foundation for the development of tailored acupuncture interventions based on TCM syndromes for managing pain in SCD. Larger samples are required to further refine and validate TCM diagnostic criteria for SCD.

Depressive and Insomnia Symptoms Sequentially Mediate the Association Between Racism-Based Discrimination in Healthcare Settings and Clinical Pain Among Adults With Sickle Cell Disease

Racism-based discrimination in healthcare settings has been associated with clinical pain in adults living with sickle cell disease; however, no studies have examined depressive and insomnia symptoms as mechanisms that may drive this relationship. This secondary data analysis examined associations between depressive and insomnia symptoms, racism-based discrimination, and clinical pain. Seventy-one adults with sickle cell disease (70% female, Mage = 38.79) provided baseline reports of racism-based discrimination, depressive symptoms, insomnia symptoms, and pain (severity, interference, catastrophizing), and they completed daily diaries of pain severity and interference over 3 months. In a sequential mediation model, baseline depressive (1st) and insomnia symptoms (2nd) significantly mediated the association between racism-based discrimination and baseline pain interference, average daily diary pain severity, and average daily diary pain interference. Although the mediation model with baseline pain severity as the outcome was significant, the total and direct effects were not. Results indicate that discrimination in healthcare settings contributes to depression, which may act on pain through sleep disturbance. Findings support the need for systemic and structural changes to eliminate discrimination in healthcare settings and behavioral mood and sleep interventions to reduce the impact of discrimination on clinical pain. PERSPECTIVE: The relationship between discrimination in healthcare settings and pain in adults with sickle cell disease may be driven by depression and sleep disturbance, modifiable risk factors and potential treatment targets. Results suggest that systemic, structural, and institutional changes must be implemented to promote better patient care and health outcomes.

Evaluating Associations between Average Pain Intensity and Genetic Variation in People with Sickle Cell Disease: An Exploratory Study

BACKGROUND

Pain is one of the most common and deleterious symptoms experienced by individuals with sickle cell disease (SCD). There is a paucity of studies identifying potential genetic mechanisms of pain in this population.

AIM

Examine associations between 11 functional single nucleotide polymorphisms in 9 candidate genes with reports of average pain intensity in individuals with sickle cell disease.

METHOD

Cross-sectional analyses were performed on data and blood samples collected through the Duke SCD Implementation Consortium Registry. Participants were asked to rate their pain "on the average" using an 11-point numeric rating scale (0 = no pain; 10 = pain as bad as you can imagine). We genotyped 11 single nucleotide polymorphisms in 9 pain-related genes using TaqMan® Genotyping Assays. Associations between each polymorphism and reports of average pain were evaluated.

RESULTS

The 86 participants (mean age: 28.7 years; 64% female) included in this study reported moderate pain on average (Mean = 4, Standard Deviation = 2.4). ICAM1 rs1799969 was the only genetic polymorphism that was significantly associated with pain (p = .01). Individuals with one or more minor alleles had lower average pain (Mean = 1.25, Standard Deviation = 1.50) than individuals without a minor allele (Mean = 4.13, Standard Deviation = 2.25). The effect size for ICAM1 rs1799969 was 1.30, which is considered large. The effect sizes for all other single nucleotide polymorphisms ranged from small to medium (range: 0-0.3).

CONCLUSIONS

Our findings provide preliminary evidence that the minor allele in ICAM1 rs1799969 had protective effects against experiencing more severe pain in sickle cell disease.

Analysis of AVPR1A, thermal and pressure pain thresholds, and stress in sickle cell disease

Aim

In patients with sickle cell disease (SCD), negative physical and emotional experiences result from intense chronic and acute pain episodes, but factors underlying these, and their interactions, are not well understood. The arginine vasopressin receptor 1a gene (AVPR1A) single nucleotide polymorphism rs10877969 has been previously associated with aspects of acute pain and stress related pain. In this study, we tested for associations between this SNP, thermal and pressure pain thresholds, clinical pain, and stress in people with SCD.

Methods

150 adults enrolled with SCD completed pain intensity measures (Average Pain Intensity, API) and the Perceived Stress Questionnaire (PSQ). Thermal and pressure pain threshold data were available from quantitative sensory testing (QST), and rs10877969 genotypes were obtained.

Results

In models adjusted for age and gender, between rs10877969 genotypes, we observed no significant differences in thermal (cold, p = 0.66; heat, p = 0.91) and mechanical (pressure, p = 0.33) pain thresholds. The association of rs10877969 with API (p = 0.09) was borderline, but non-significant with PSQ (p = 0.51). The correlation between clinical pain and environmental stress was significant, r = 0.18, p = 0.024, however, the interaction of genotype and PSQ was not significant (p = 0.63).

Conclusion

Clinical and experimental pain were not significantly associated with the rs10877969 genotype. The rs10877969 genotype did not moderate the correlation between environmental stress and clinical pain in this population. However, a trend toward a protective T allele effect on average pain rating in SCD warrants future exploration of this SNP/gene in SCD.

Sickle cell disease chronic joint pain: Clinical assessment based on maladaptive central nervous system plasticity

Chronic joint pain (CJP) is among the significant musculoskeletal comorbidities in sickle cell disease (SCD) individuals. However, many healthcare professionals have difficulties in understanding and evaluating it. In addition, most musculoskeletal evaluation procedures do not consider central nervous system (CNS) plasticity associated with CJP, which is frequently maladaptive. This review study highlights the potential mechanisms of CNS maladaptive plasticity related to CJP in SCD and proposes reliable instruments and methods for musculoskeletal assessment adapted to those patients. A review was carried out in the PubMed and SciELO databases, searching for information that could help in the understanding of the mechanisms of CNS maladaptive plasticity related to pain in SCD and that presented assessment instruments/methods that could be used in the clinical setting by healthcare professionals who manage chronic pain in SCD individuals. Some maladaptive CNS plasticity mechanisms seem important in CJP, including the impairment of pain endogenous control systems, central sensitization, motor cortex reorganization, motor control modification, and arthrogenic muscle inhibition. Understanding the link between maladaptive CNS plasticity and CJP mechanisms and its assessment through accurate instruments and methods may help healthcare professionals to increase the quality of treatment offered to SCD patients.

Sleep, Positive Affect, and Circulating Interleukin-6 in Women With Temporomandibular Joint Disorder

OBJECTIVE

Systemic inflammation is commonly observed in idiopathic chronic pain conditions, including temporomandibular joint disorder (TMD). Trait positive affect (PA) is associated with lower inflammation in healthy controls, but those effects may be threatened by poor sleep. The associations between PA with proinflammatory cytokine activity and potential moderation by sleep in chronic pain are not known. We thus investigated the association between PA and circulating interleukin-6 (IL-6) and moderation of that association by sleep in a sample of women with TMD and sleep difficulties.

METHODS

Participants (n = 110) completed the insomnia severity index and provided blood samples at five intervals throughout an evoked pain testing session. They then completed a 14-day diary assessing sleep and affect, along with wrist actigraphy.

RESULTS

There was not a significant main effect of PA on resting or pain-evoked IL-6 (b = 0.04, p = .33). Diary total sleep time (b = -0.002, p = .008), sleep efficiency (b = -0.01, p = .005), sleep onset latency (b = 0.006, p = .010), and wake after sleep onset (b = 0.003, p = .033) interacted with PA to predict IL-6, such that PA inversely predicted IL-6 at higher levels of total sleep time and sleep efficiency and at lower levels of sleep onset latency and wake after sleep onset. Surprisingly, when sleep was poor, PA predicted greater IL-6.

CONCLUSIONS

The potential salutary effects of PA on resting IL-6 erode when sleep is poor, underscoring the importance of considering sleep in conceptual and intervention models of TMD.

Severe Persistent Pain and Inflammatory Biomarkers in Sickle Cell Disease: An Exploratory Study

BACKGROUND

Severe pain is among the most common and deleterious symptoms experienced by individuals with sickle cell disease (SCD), of whom more than 50% report chronic pain. Despite this, the understanding of the biological contributors to persistent severe SCD pain is limited. This exploratory study sought to describe pain phenotypes based on frequency of severe pain experienced over 6 months and identify inflammatory biomarkers associated with pain phenotypes among individuals with SCD.

METHODS

This study used self-report and electronic health record data collected from 74 individuals enrolled in the Duke Sickle Cell Disease Implementation Consortium Registry. Plasma from previously collected blood specimens was used to generate inflammatory biomarker data using the Inflammation 20-plex ProcartaPlexTM panel. Descriptive statistics were used to describe the occurrence of severe pain over the past 6 months, and bi-variate analyses were used to evaluate the relationship between inflammatory biomarkers and pain phenotypes.

RESULTS

Among the 74 participants included in this study, 33.8% reported severe pain occurring never or rarely, 40.5% reported severe pain occurring sometimes, and 25.7% reported severe pain occurring often or always. Soluble E-selectin (sE-selectin) was the only inflammatory biomarker significantly associated with the pain phenotype groups (p = 0.049). Post hoc comparisons identified that participants in the often/always severe pain group had significantly higher plasma concentrations of sE-selectin compared to those in the sometimes severe pain group (p = 0.040).

CONCLUSIONS

Our findings provide preliminary evidence of the frequent occurrence of severe pain and that sE-selectin may be an objective biomarker for the frequent occurrence of severe pain in this population.

Pain in sickle cell disease: current and potential translational therapies

Pain is a major comorbidity of sickle cell disease (SCD). Patients with SCD may suffer from both acute and chronic pain. Acute pain is caused by recurrent and unpredictable episodes of vaso-occlusive crises (VOC), whereas the exact etiology of chronic pain is still unknown. Opioids are the mainstay for pain treatment, but the opioid epidemic has significantly altered access to prescription opioids and has brought concerns over their long-term use into the forefront, which have negatively impacted the treatment of sickle pain. Opioids remain potent analgesics but growing opioid-phobia has led to the realization of an unmet need to develop nonopioid therapies that can provide relief for severe sickle pain. This realization has contributed to the approval of 3 different drugs by the Food and Drug Administration (FDA) for the treatment of SCD, particularly to reduce VOC and/or have an impact on the pathobiology of SCD. In this review, we outline the challenges and need for validation of side-effects of opioids and provide an update on the development of mechanism-based translational therapies, specifically targeting pain in SCD.

Characteristics of sickle cell patients with frequent emergency department visits and hospitalizations

Vaso-occlusive episodes (VOEs) are a hallmark of sickle cell disease (SCD), and account for >90% of health care encounters for this patient population. The Cooperative Study of Sickle Cell Disease, a large study enrolling >3000 patients, showed that the majority of SCD patients (80%) experienced 0–3 major pain crises/year. Only a small minority (~5%) experienced ≥6 VOEs/year. Our study sought to further understand this difference in VOE frequency between SCD patients. We analyzed 25 patients (13M/12F, mean age of 28.8) with ≥6 ED visits or hospitalizations/year (high utilizers), and compared these with 9 patients (6M/3F, mean age of 37.6) who had ≤2 ED visits or hospitalizations/year (low utilizers). All subjects were given a demographic survey along with questionnaires for depression, anxiety, and Health Locus of Control. Each subject then underwent quantitative sensory testing (QST) with three different modalities: pressure pain sensitivity, heat and cold sensitivity, and Von Frey monofilament testing. Laboratory and clinical data were collected through subjects’ medical records. CBC and chemistry analysis showed high utilizers had higher WBC (p<0.01), ANC (p<0.01), total bilirubin (p = 0.02), and lower MCV (p = 0.03). Opioid use (morphine equivalents) over the past 6 months was significantly higher in the high utilizer group (12125.7 mg vs 2423.1 mg, p = 0.005). QST results showed lower pressure pain threshold at the ulna (224.4 KPa vs 338.9 KPa, p = 0.04) in the high utilizer group. High utilizers also had higher anxiety (9.0 vs 4.6, p = 0.04) and depression scores (10.0 vs 6.0, p = 0.051). While the low utilizer group had higher education levels with more associate and bachelor degrees (p = 0.009), there was no difference in income or employment. These data show that many biological and psychosocial factors contribute to high health care utilization in SCD. A multi-disciplinary and multi-faceted approach will be required to address this complex problem.

Considerations for Cannabis Use to Treat Pain in Sickle Cell Disease

Pain in Sickle Cell Disease (SCD) is a major comorbidity and unique with acute pain due to recurrent and episodic vaso-occlusive crises as well as chronic pain, which can span an individual's entire life. Opioids are the mainstay treatment for pain in SCD. Due to recent health crises raised by adverse effects including deaths from opioid use, pain management in SCD is adversely affected. Cannabis and its products are most widely used for pain in multiple conditions and also by patients with SCD on their own. With the availability of "Medical Cannabis" and approval to use cannabis as medicine across majority of States in the United States as well as over-the-counter preparations, cannabis products are being used increasingly for SCD. The reliability of many of these products remains questionable, which poses a major health risk to the vulnerable individuals seeking pain relief. Therefore, this review provides up to date insights into available categories of cannabis-based treatment strategies, their mechanism of action and pre-clinical and clinical outcomes in SCD. It provides evidence for the benefits and risks of cannabis use in SCD and cautions about the unreliable and unvalidated products that may be adulterated with life-threatening non-cannabis compounds.

Spatiotemporal Alterations in Gait in Humanized Transgenic Sickle Mice

Sickle cell disease (SCD) is a hemoglobinopathy affecting multiple organs and featuring acute and chronic pain. Purkinje cell damage and hyperalgesia have been demonstrated in transgenic sickle mice. Purkinje cells are associated with movement and neural function which may influence pain. We hypothesized that Purkinje cell damage and/or chronic pain burden provoke compensatory gait changes in sickle mice. We found that Purkinje cells undergoe increased apoptosis as shown by caspase-3 activation. Using an automated gait measurement system, MouseWalker, we characterized spatiotemporal gait characteristics of humanized transgenic BERK sickle mice in comparison to control mice. Sickle mice showed alteration in stance instability and dynamic gait parameters (walking speed, stance duration, swing duration and specific swing indices). Differences in stance instability may reflect motor dysfunction due to damaged Purkinje cells. Alterations in diagonal and all stance indices indicative of hesitation during walking may originate from motor dysfunction and/or arise from fear and/or anticipation of movement-evoked pain. We also demonstrate that stance duration, diagonal swing indices and all stance indices correlate with both mechanical and deep tissue hyperalgesia, while stance instability correlates with only deep tissue hyperalgesia. Therefore, objective analysis of gait in SCD may provide insights into neurological impairment and pain states.

Characteristics and potential biomarkers of adult sickle cell patients with chronic pain

OBJECTIVES

In this study, we investigated the evolution of chronic pain in sickle cell patients (SCD) as an age-dependent phenomenon and studied the frequency of vaso-occlusive episode frequency, opioid use, quantitative sensory testing (QST), and biomarkers of chronic pain (CP).

METHODS

We undertook a cross-sectional study of the evolution of CP in SCD. A total of 72 subjects (age 15-66) were enrolled. VOE frequency, presence of CP hydroxyurea (HU) therapy, opioid use, and laboratory parameters were collected. QST was performed, and plasma tryptase, substance P, and NGF (Nerve Growth Factor) levels were assayed.

RESULTS

There was an age-dependent increase in frequency of CP, VOEs, opioid use, and Von Frey monofilament values. CP patients had significantly higher opioid use (daily morphine equivalents) (52.8 mg vs 6.94 mg, P = .009), suggesting a correlation between opioid use and hyperalgesia. NGF levels were also significantly higher (P = .051). Our results confirm previous observations of an age-dependent increase in the proportion of patients with CP and support the contributing role of mast cell activation and neurogenic inflammation.

CONCLUSIONS

This is the first study of NGF as a possible biomarker of CP in SCD. If confirmed, this could provide a diagnostic marker and therapeutic target for CP in SCD.

Sex Differences in Interleukin-6 Responses Over Time Following Laboratory Pain Testing Among Patients With Knee Osteoarthritis

Epidemiological studies suggest that women are not only at a higher risk for developing knee osteoarthritis (KOA), but also report greater symptom severity compared to men. One potential underlying mechanism of these sex differences may be exaggerated inflammatory responses to pain among women compared to men. The present study examined sex differences in interleukin-6 (IL-6) response over time following experimental pain testing. We hypothesized that women, when compared to men, would show greater IL-6 reactivity when exposed to acute pain in a human laboratory setting. Eighty-four participants (36 men and 48 women) with KOA scheduled for total knee arthroplasty underwent a quantitative sensory testing (QST) battery. A total of seven IL-6 measurements were taken, twice at baseline, once immediately after QST, and every 30 minutes up to 2 hours after QST. Consistent with our hypothesis, women, when compared to men, showed accelerated increases in IL-6 levels following laboratory-evoked pain, even after controlling for body mass index, marital status, clinical pain, evoked pain sensitivity, and situational pain catastrophizing. Given that KOA is a chronic condition, and individuals with KOA frequently experience pain, these sex differences in IL-6 reactivity may contribute to the maintenance and/or exacerbation of KOA symptoms. PERSPECTIVES: The present study demonstrates that women, when compared to men, exhibit greater IL-6 reactivity after exposure to laboratory-evoked pain. Such sex differences may explain the mechanisms underlying women's higher chronic pain risk and pain perception, as well as provide further insight in developing personalized pain interventions.

Autonomically-mediated decrease in microvascular blood flow due to mental stress and pain in sickle cell disease: A target for neuromodulatory interventions

Pain and vaso-occlusive crises (VOC) are hallmark complications of sickle cell disease (SCD) and result in significant physical and psychosocial impairment. The variability in SCD pain frequency and triggers for the transition from steady state to VOC are not well understood. This paper summarizes the harmful physiological effects of pain and emotional stressors on autonomically-mediated vascular function in individuals with SCD and the effects of a cognitive, neuromodulatory intervention (i.e. hypnosis) on microvascular blood flow. We reviewed recent studies from the authors' vascular physiology laboratory that assessed microvascular responses to laboratory stressors in individuals with SCD. Results indicate that participants with SCD exhibit marked neurally mediated vascular reactivity in response to pain, pain-related fear, and mental stress. Further, pilot study results show that engagement in hypnosis may attenuate harmful microvascular responses to pain. The collective results demonstrate that autonomically-mediated vascular responses to pain and mental stress represent an important SCD intervention target. This ongoing work provides physiological justification for the inclusion of cognitive, neuromodulatory and complementary treatments in SCD disease management and may inform the development of targeted, integrative interventions that prevent the enhancement of autonomic vascular dysfunction in SCD.

End points for sickle cell disease clinical trials: patient-reported outcomes, pain, and the brain

To address the global burden of sickle cell disease (SCD) and the need for novel therapies, the American Society of Hematology partnered with the US Food and Drug Administration to engage the work of 7 panels of clinicians, investigators, and patients to develop consensus recommendations for clinical trial end points. The panels conducted their work through literature reviews, assessment of available evidence, and expert judgment focusing on end points related to: patient-reported outcomes (PROs), pain (non-PROs), the brain, end-organ considerations, biomarkers, measurement of cure, and low-resource settings. This article presents the findings and recommendations of the PROs, pain, and brain panels, as well as relevant findings and recommendations from the biomarkers panel. The panels identify end points, where there were supporting data, to use in clinical trials of SCD. In addition, the panels discuss where further research is needed to support the development and validation of additional clinical trial end points.

Relationship of Pain Quality Descriptors and Quantitative Sensory Testing: Sickle Cell Disease

BACKGROUND

Chronic pain in adults with sickle cell disease (SCD) may be the result of altered processing in the central nervous system, as indicated by quantitative sensory testing (QST). Sensory pain quality descriptors on the McGill Pain Questionnaire (MPQ) are indicators of typical or altered pain mechanisms but have not been validated with QST-derived classifications.

OBJECTIVES

The specific aim of this study was to identify the sensory pain quality descriptors that are associated with the QST-derived normal or sensitized classifications. We expected to find that sets of sensory pain quality descriptors would discriminate the classifications.

METHODS

A cross-sectional quantitative study of existing data from 186 adults of African ancestry with SCD. Variables included MPQ descriptors, patient demographic data, and QST-derived classifications.

RESULTS

The participants were classified as central sensitization (n = 33), mixed sensitization (n = 23), and normal sensation. Sensory pain quality descriptors that differed statistically between mixed sensitization and central sensation compared to normal sensitization included cold (p = .01) and spreading (p = .01). Aching (p = .01) and throbbing (p = .01) differed statistically between central sensitization compared with mixed sensitization and normal sensation. Beating (p = .01) differed statistically between mixed sensitization compared with central sensitization and normal sensation. No set of sensory pain quality descriptors differed statistically between QST classifications.

DISCUSSION

Our study is the first to examine the association between MPQ sensory pain quality descriptors and QST-derived classifications in adults with SCD. Our findings provide the basis for the development of a MPQ subscale with potential as a mechanism-based screening tool for neuropathic pain.

Sensitivities to Thermal and Mechanical Stimuli: Adults With Sickle Cell Disease Compared to Healthy, Pain-Free African American Controls

Evidence supports^, but is inconclusive that sensitization contributes to chronic pain in some adults with sickle cell disease (SCD). We determined the prevalence of pain sensitization among adults with SCD pain compared with pain-free healthy adults. In a cross sectional, single session study of 186 African American outpatients with SCD pain (age 18-74 years, 59% female) and 124 healthy age, gender, and race matched control subjects (age 18-69 years, 49% female), we compared responses to standard thermal (Medoc TSA II) and mechanical stimuli (von Frey filaments). Although we observed no significant differences in thermal thresholds between controls and patients, patients with SCD had lower pain thresholds to mechanical stimuli and reported higher pain intensity scores to all thermal and mechanical stimuli at a non-painful body site. Compared with controls, about twice as many patients with SCD showed sensitization: 12% versus 23% at the anterior forearm site (P = .02), and 16% versus 32% across 3 tested sites (P = .004). Among patients with SCD, 18% exhibited some element of central sensitization. Findings indicate that persistent allodynia and hyperalgesia can be part of the SCD pain experience and should be considered when selecting therapies for SCD pain. PERSPECTIVE: Compared with matched healthy controls, quantitative sensory testing in adults with pain and sickle cell disease (SCD) demonstrates higher prevalence of sensitization, including central sensitization. The findings of allodynia and hyperalgesia may indicate neuropathic pain and could contribute to a paradigm shift in assessment and treatment of SCD pain.

A QST-based Pain Phenotype in Adults With Sickle Cell Disease: Sensitivity and Specificity of Quality Descriptors

BACKGROUND

We sought to refine a screening measure for discriminating a sensitized or normal sensation pain phenotype among African American adults with sickle cell disease (SCD).

OBJECTIVE

To develop scoring schemes based on sensory pain quality descriptors; evaluate their performance on classifying patients with SCD who had sensitization or normal sensation, and compare with scores on the Self-report Leeds Assessment of Neuropathic Symptoms and Signs (S-LANSS) and the Neuropathic Pain Symptom Inventory (NPSI).

METHODS

Participants completed PAINReportIt, quantitative sensory testing (QST), S-LANSS, and NPSI. Conventional binary logistic regression and least absolute shrinkage and selection operator (lasso) regression were used to obtain 2 sets of weights resulting in 2 scores: the PR-Logistic (PAINReportIt score weighted by conventional binary logistic regression coefficients) and PR-Lasso (PAINReportIt score weighted by lasso regression coefficients). Performance of the proposed scores and the existing scores were evaluated.

RESULTS

Lasso regression resulted in a parsimonious model with non-zero weights assigned to 2 neuropathic descriptors, cold and spreading. We found positive correlations between the PR-Lasso and other scores: S-LANSS (r = 0.22, P < 0.01), NPSI (r = 0.22, P < 0.01), and PR-Logistic (r = 0.35, P < 0.01). The NPSI and PR-Lasso performed similarly at different levels of required specificity and outperformed the S-LANSS and PR-Logistic at the various specificity points.

CONCLUSION

The PR-Lasso offers a way to discriminate a SCD pain phenotype.

Thermal and mechanical quantitative sensory testing values among healthy African American adults

PURPOSE

Only a few studies have reported quantitative sensory testing (QST) reference values for healthy African Americans, and those studies are limited in sample size and age of participants. The study purpose was to characterize QST values in healthy, pain-free African American adults and older adults whose prior pain experiences and psychological status were also measured. We examined the QST values for differences by sex, age, and body test site.

PATIENTS AND METHODS

A cross-sectional sample of 124 pain-free African American adults (age 18-69 years, 49% female) completed demographic and self-reported pain, fatigue and psychosocial measures. QST was performed to obtain thermal and mechanical responses and associated pain intensity levels.

RESULTS

We found thermal detection values at the anterior forearm were (29.2 °C±1.6) for cool detection (CD) and (34.5 °C±1.2) for warm detection (WD). At that site the sample had cold pain threshold (CPTh) (26.3 °C±5.0), heat pain threshold (HPTh) (37.8 °C±3.6), and mechanical pain thresholds (MPTH) (16.7±22.2 grams of force, gF). There was a significant between sex difference for WD, with women being more sensitive (q=0.027). Lower body sites were less sensitive than upper body sites across all thermal modalities (q<0.003), but not for the mechanical modality.

CONCLUSION

The QST values from this protocol at the anterior forearm indicate that the healthy African American adults had average thermal pain thresholds close to the temperature of adaptation and average MPTh under 20 gF. Differences in responses to thermal and mechanical stimuli for upper verses lower body were consistent with prior research.

Sensitization of nociceptors and dorsal horn neurons contributes to pain in sickle cell disease

Sickle cell disease (SCD) describes a group of disorders associated with a point mutation in the beta chain of hemoglobin. The mutation leads to the creation of sickle hemoglobin (HbS) and causes distortion of erythrocytes through polymerization under low oxygen, resulting in characteristic sickle red blood cells. Vaso-occlusion episodes caused by accumulation of sRBCs results in ischemia-reperfusion injury, reduced oxygen supply to organs, oxidative stress, organ damage and severe pain that often requires hospitalization and opioid treatment. Further, many patients suffer from chronic pain, including hypersensitivity to heat and cold stimuli. Progress towards the development of novel strategies for both acute and chronic pain in patients with SCD has been impeded by a lack of understanding the mechanisms underlying pain in SCD. The purpose of this review is to highlight evidence for the contribution of peripheral and central sensitization that leads to widespread, chronic pain and hyperalgesia. Targeting the mechanisms that initiate and maintain sensitization in SCD might offer effective approaches to manage the severe and debilitating pain associated with this condition.

Quantitative sensory testing in children with sickle cell disease: additional insights and future possibilities

Quantitative sensory testing (QST) is used in a variety of pain disorders to characterize pain and predict prognosis and response to specific therapies. In this study, we aimed to confirm results in the literature documenting altered QST thresholds in sickle cell disease (SCD) and assess the test-retest reliability of results over time. Fifty-seven SCD and 60 control subjects aged 8-20 years underwent heat and cold detection and pain threshold testing using a Medoc TSAII. Participants were tested at baseline and 3 months; SCD subjects were additionally tested at 6 months. An important facet of our study was the development and use of a novel QST modelling approach, allowing us to model all data together across modalities. We have not demonstrated significant differences in thermal thresholds between subjects with SCD and controls. Thermal thresholds were consistent over a 3- to 6-month period. Subjects on whom hydroxycarbamide (HC) was initiated shortly before or after baseline testing (new HC users) exhibited progressive decreases in thermal sensitivity from baseline to 6 months, suggesting that thermal testing may be sensitive to effective therapy to prevent vasoocclusive pain. These findings inform the use of QST as an endpoint in the evaluation of preventative pain therapies.

Preliminary evidence that hydroxyurea is associated with attenuated peripheral sensitization in adults with sickle cell disease

Introduction:

Hydroxyurea (HU) is a drug that targets the underlying pathophysiology of sickle cell disease (SCD); however, it continues to be an underutilized treatment for adults. Previous research suggests that HU treatment can result in fewer hospital contacts for acute vaso-occlusive pain crises (VOC). Hydroxyurea's impact on non-VOC pain, however, is not well established.

Objectives:

This study examined whether HU moderated patterns of static and dynamic pain processing and clinical pain in SCD individuals.

Methods:

Fifty-eight patients with SCD (N taking HU = 17) underwent quantitative sensory testing (QST) and completed twice daily symptom diaries for 12 weeks. Quantitative sensory testing established thermal threshold and tolerance, mechanical thresholds, and thermal and mechanical temporal summation of pain.

Results:

Groups did not differ in age, sex, or opioid use. After controlling for morphine use, QST results showed that participants taking HU had higher heat and mechanical pain thresholds (static QST measures) but not thermal and mechanical temporal summation (dynamic QST measures). Participants taking HU also reported lower VOC pain compared with SCD participants not taking HU; however, HU did not moderate non-VOC clinical pain ratings.

Conclusion:

Findings cautiously suggest that HU acts on pain hypersensitivity and VOC pain, rather than inhibiting pain facilitation and non-VOC pain. These differences may reflect HU's influence on peripheral rather than central sensitization. Future research is warranted to replicate these findings in a larger sample and determine whether early HU administration can prevent peripheral sensitization in SCD individuals.

Mast Cells Induce Blood Brain Barrier Damage in SCD by Causing Endoplasmic Reticulum Stress in the Endothelium

Endothelial dysfunction underlies the pathobiology of cerebrovascular disease. Mast cells are located in close proximity to the vasculature, and vasoactive mediators released upon their activation can promote endothelial activation leading to blood brain barrier (BBB) dysfunction. We examined the mechanism of mast cell-induced endothelial activation via endoplasmic reticulum (ER) stress mediated P-selectin expression in a transgenic mouse model of sickle cell disease (SCD), which shows BBB dysfunction. We used mouse brain endothelial cells (mBECs) and mast cells-derived from skin of control and sickle mice to examine the mechanisms involved. Compared to control mouse mast cell conditioned medium (MCCM), mBECs incubated with sickle mouse MCCM showed increased, structural disorganization and swelling of the ER and Golgi, aggregation of ribosomes, ER stress marker proteins, accumulation of galactose-1-phosphate uridyl transferase, mitochondrial dysfunction, reactive oxygen species (ROS) production, P-selectin expression and mBEC permeability. These effects of sickle-MCCM on mBEC were inhibited by Salubrinal, a reducer of ER stress. Histamine levels in the plasma, skin releasate and in mast cells of sickle mice were higher compared to control mice. Compared to control BBB permeability was increased in sickle mice. Treatment of mice with imatinib, Salubrinal, or P-selectin blocking antibody reduced BBB permeability in sickle mice. Mast cells induce endothelial dysfunction via ER stress-mediated P-selectin expression. Mast cell activation contributes to ER stress mediated endothelial P-selectin expression leading to increased endothelial permeability and impairment of BBB. Targeting mast cells and/or ER stress has the potential to ameliorate endothelial dysfunction in SCD and other pathobiologies.

Beta2-Adrenergic Receptor Polymorphisms and Haplotypes Associate With Chronic Pain in Sickle Cell Disease

Pain in sickle cell disease (SCD) is severe, variable, and inadequately comprehended. The β2-adrenergic receptor (ADRB2) is critical in mediating neurotransmitter response in the sympathetic nervous system. In this association study, we examined 16 single nucleotide polymorphisms (SNPs) covering 5'-UTR and coding regions of ADRB2 for pain variability in SCD. Subjects recorded their non-crisis, baseline pain experience on a computerized tool from which we obtained chronic pain measurement score- composite pain index (CPI). Regression models yielded significant associations between chronic pain and seven SNPs. Non-synonymous SNP rs1042713 A allele (Arg16) caused a 5.73-fold decrease in CPI (p = 0.002). Allele A of rs12654778 and T of rs17778257 reduced CPI by a fold of 4.52 (p = 0.019), and 4.39 (p = 0.032), respectively. Whereas, in the 5' UTR, allele C of rs1042711, G of rs11168070, C of rs11959427, and C of rs1801704 increased CPI by a fold of 10.86 (p = 0.00049), 5.99 (p = 0.016), 5.69 (p = 0.023), and 5.26 (p = 0.031), respectively. Together, these SNPs accounted for 2-15% of CPI variance after adjusting for covariates. Moreover, these SNPs were in high linkage disequilibrium (LD) showing three LD blocks in our cohort. A 10-marker haplotype increased CPI by 11.5-fold (p = 0.000407). Thus, ADRB2 polymorphisms might contribute to chronic pain severity and heterogeneity in SCD.

Association Between Pain Sensitization and Disease Activity in Patients With Rheumatoid Arthritis: A Cross-Sectional Study

OBJECTIVE

Pain sensitization may contribute to pain severity in rheumatoid arthritis (RA), impacting disease activity assessment. We examined whether pain processing mechanisms were associated with disease activity among RA patients with active disease.

METHODS

The study included 139 subjects enrolled in the Central Pain in Rheumatoid Arthritis cohort. Subjects underwent quantitative sensory testing (QST), including assessment of pressure pain thresholds (PPTs) at multiple sites, conditioned pain modulation, and temporal summation. RA disease activity was assessed using the Clinical Disease Activity Index (CDAI) and its components. We examined cross-sectional associations between QST measures and disease activity using linear regression.

RESULTS

Low PPTs (high pain sensitization) at all sites were associated with high CDAI scores (P ≤ 0.03) and tender joint counts (P ≤ 0.002). Associations between PPTs and patient global assessments were also seen at most sites. High temporal summation at the forearm (also reflecting high pain sensitization) was significantly associated with high CDAI scores (P = 0.02), patient global assessment scores (P = 0.0006), evaluator global assessment scores (P = 0.01), and tender joint counts (P = 0.02). Conversely, conditioned pain modulation (a measure of descending inhibitory pain pathways) was associated only with tender joint count (P = 0.03).

CONCLUSION

High pain sensitization is associated with elevations in disease activity measures. Longitudinal studies are underway to elucidate the cause-effect relationships between pain sensitization and inflammatory disease activity in RA.

Mouse Models of Pain in Sickle Cell Disease

Sickle cell disease (SCD) is a genetic blood disorder that impacts millions of individuals worldwide. SCD is characterized by debilitating pain that can begin during infancy and may continue to increase throughout life. This pain can be both acute and chronic. A characteristic feature specific to acute pain in SCD occurs during vaso-occlusive crisis (VOC) due to the blockade of capillaries with sickle red blood cells. The acute pain of VOC is intense, unpredictable, and requires hospitalization. Chronic pain occurs in a significant population with SCD. Treatment options for sickle pain are limited and primarily involve the use of opioids. However, long-term opioid use is associated with numerous side effects. Thus, pain management in SCD remains a major challenge. Humanized transgenic mice expressing exclusively human sickle hemoglobin show features of pain and pathobiology similar to that in patients with SCD. Therefore, these mice offer the potential for investigating the mechanisms of pain in SCD and allow for development of novel targeted analgesic therapies. © 2018 by John Wiley & Sons, Inc.

Pressure Pain Phenotypes in Women Before Breast Cancer Treatment

OBJECTIVES

To explore associations between quantitative sensory testing (QST) and pretreatment pain, physical, and psychological characteristics in women with breast cancer.

SAMPLE & SETTING

41 women with treatment-naive stage 0-III breast cancer at the University of Michigan Comprehensive Cancer Center in Ann Arbor.

METHODS & VARIABLES

Participants completed self-report surveys and QST within the month before breast surgery. Pressure pain thresholds (PPTs) were measured bilaterally at each trapezius with a manual QST algometer. PPT values were split, yielding low, moderate, and high pain sensitivity subgroups. Subgroup self-reported characteristics were compared using Spearman's correlation, chi-square, and one-way analysis of variance.

RESULTS

Lower PPT (higher sensitivity) was associated with higher levels of pain interference and maladaptive pain cognitions. The high-sensitivity group reported higher pain severities, interference, and catastrophizing and lower belief in internal locus of pain control than the low-sensitivity group.

IMPLICATIONS FOR NURSING

Individualized interventions for maladaptive pain cognitions before surgery may reduce pain sensitivity and the severity of chronic pain developed after surgery.

Bivalent ligand MCC22 potently attenuates nociception in a murine model of sickle cell disease

Sickle cell disease (SCD) is a chronic inflammatory disorder accompanied by chronic pain. In addition to ongoing pain and hyperalgesia, vaso-occlusive crises-induced pain can be chronic or episodic. Because analgesics typically used to treat pain are not very effective in SCD, opioids, including morphine, are a primary treatment for managing pain in SCD but are associated with many serious side effects, including constipation, tolerance, addiction, and respiratory depression. Thus, there is a need for the development of novel treatments for pain in SCD. In this study, we used the Townes transgenic mouse model of SCD to investigate the antinociceptive efficacy of the bivalent ligand, MCC22, and compared its effectiveness with morphine. MCC22 consists of a mu-opioid receptor agonist and a chemokine receptor-5 (CCR5) antagonist that are linked through a 22-atom spacer. Our results show that intraperitoneal administration of MCC22 produced exceptionally potent dose-dependent antihyperalgesia as compared to morphine, dramatically decreased evoked responses of nociceptive dorsal horn neurons, and decreased expression of proinflammatory cytokines in the spinal cord. Moreover, tolerance did not develop to its analgesic effects after repeated administration. In view of the extraordinary potency of MCC22 without tolerance, MCC22 and similar compounds may vastly improve the management of pain associated with SCD.

Quantitative sensory testing is feasible and is well-tolerated in patients with sickle cell disease following a vaso-occlusive episode

Introduction

Sickle cell disease (SCD) is an inherited blood disorder characterized by abnormally shaped sickle cells. The hallmark of this disease is intermittent, painful vaso-occlusive episodes (VOE), but a subset of individuals with SCD experience chronic pain. The mechanism of transition to chronic pain is not well understood in SCD, but there is evidence of altered pain processing in individuals with SCD. The impact of VOE on pain sensitivity is not established. The objective of this study was to determine the feasibility and tolerability of quantitative sensory testing (QST) in SCD following a VOE to better understand the contribution of VOE to the development of chronic pain.

Methods

As part of a larger pain sensitivity study, pediatric patients with SCD were offered QST following a VOE-related Emergency Room visit or inpatient hospitalization. The feasibility of recruitment and completion of QST was measured, and tolerability of QST was determined using post-QST assessments of pain, and compared with measurements at steady state.

Results

Ten participants completed QST following a VOE. The median age was 16.5, and 60% were female. Overall, 10 of 16 (62.5%) patients approached for QST following VOE completed QST. This included 8 of 12 patients who had previously completed QST at steady state. There were no statistically significant differences in pain intensity and Gracely Box scores after QST following a VOE, when compared to steady-state QST.

Conclusion

QST is feasible and is well-tolerated following a VOE in patients with SCD. Large prospective studies are needed to determine the impact of VOE on experimental pain sensitivity and must take into account all factors contributing to pain sensitivity.

Daily Opioid Use Fluctuates as a Function of Pain, Catastrophizing, and Affect in Patients With Sickle Cell Disease: An Electronic Daily Diary Analysis

Chronic opioid therapy is a common treatment regimen for patients with sickle cell disease (SCD), a chronically painful recessive hemoglobinopathy. The collective risk profile of chronic opioid therapy necessitates an understanding of which pain-related factors, such as affect and pain catastrophizing, are associated with the ebbs and flows of opioid use in daily life, a topic that has received very little attention among patients with any type of chronically painful condition, including SCD. We therefore investigated the variability of day-to-day patterns of short- and long-acting opioid use and their associations with pain and pain-related cognitive and affective processes in daily life among patients with SCD using a nightly electronic diary (N = 45). Opioid use was self-reported and converted into oral morphine equivalents for analysis, which was conducted with mixed effects modeling. Results indicated that greater pain and pain catastrophizing were associated with greater use of short-acting opioids, and negative affect was associated with greater use of long-acting opioids. Additionally, the association of pain and short-acting opioid use was moderated by pain catastrophizing, showing that opioid use was elevated when patients catastrophized about their pain, even if they reported low levels of pain. These findings suggest that monitoring pain-related cognitive and affective variables may be a useful approach to understanding risk for problematic opioid use in patients with daily pain.

PERSPECTIVE

The present study shows that pain and pain-related cognitive and affective variables are associated with daily variation in prescription opioid use in SCD. The findings may have broad implications for tracking and defining risk for prescription opioid misuse in patients with daily pain.

Increased theta band EEG power in sickle cell disease patients

Objective

Pain is a major issue in the care of patients with sickle cell disease (SCD). The mechanisms behind pain and the best way to treat it are not well understood. We studied how electroencephalography (EEG) is altered in SCD patients.

Methods

We recruited 20 SCD patients and compared their resting state EEG to that of 14 healthy controls. EEG power was found across frequency bands using Welch's method. Electrophysiological source imaging was assessed for each frequency band using the eLORETA algorithm.

Results

SCD patients had increased theta power and decreased beta2 power compared to controls. Source localization revealed that areas of greater theta band activity were in areas related to pain processing. Imaging parameters were significantly correlated to emergency department visits, which indicate disease severity and chronic pain intensity.

Conclusion

The present results support the pain mechanism referred to as thalamocortical dysrhythmia. This mechanism causes increased theta power in patients.

Significance

Our findings show that EEG can be used to quantitatively evaluate differences between controls and SCD patients. Our results show the potential of EEG to differentiate between different levels of pain in an unbiased setting, where specific frequency bands could be used as biomarkers for chronic pain.

Pain-measurement tools in sickle cell disease: where are we now?

Pain is a complex multidimensional experience and the most common morbidity in patients with sickle cell disease (SCD). Tools to assess pain can be of use not only to guide pain treatment but also to provide insight into underlying pain neurobiology. Mechanisms of pain in SCD are multifactorial and are not completely elucidated. Although vaso-occlusion of microcirculation by sickled red cells is believed to be the underlying mechanism of acute vaso-occlusive pain, mechanisms for chronic pain and the transition from acute to chronic pain are under investigation. A number of modalities can be used in clinical practice and/or research to capture various dimensions of pain. Selection of a pain-assessment tool should be directed by the purpose of the assessment. Pain-assessment tools, many of which are currently in the early stages of validation, are discussed here. Development and validation of these multimodal tools is crucial for developing improved understanding of SCD pain and its management.

Central sensitization associated with low fetal hemoglobin levels in adults with sickle cell anemia

BACKGROUND AND AIMS

Pain is the hallmark of sickle cell anemia (SCA), presenting as recurrent acute events or chronic pain. Central sensitization, or enhanced excitability of the central nervous system, alters pain processing and contributes to the maintenance of chronic pain. Individuals with SCA demonstrate enhanced sensitivity to painful stimuli however central mechanisms of pain have not been fully explored. We hypothesized that adults with SCA would show evidence of central sensitization as observed in other diseases of chronic pain.

METHODS

We conducted a prospective study of static and dynamic quantitative sensory tests in 30 adults with SCA and 30 matched controls.

RESULTS

Static thermal testing using cold stimuli showed lower pain thresholds (p=0.04) and tolerance (p=0.04) in sickle cell subjects, but not for heat. However, SCA subjects reported higher pain ratings with random heat pulses (p<0.0001) and change in scores with temporal summation at the heat pain threshold (p=0.002). Similarly, with the use of pressure pain stimuli, sickle cell subjects reported higher pain ratings (p=0.04), but not higher pressure pain tolerance/thresholds or allodynia to light tactile stimuli. Temporal summation pain score changes using 2 pinprick probes (256 and 512mN) were significantly greater (p=0.004 and p=0.008) with sickle cell, and delayed recovery was associated with lower fetal hemoglobin (p=0.002 and 0.003).

CONCLUSIONS

Exaggerated temporal summation responses provide evidence of central sensitization in SCA.

IMPLICATIONS

The association with fetal hemoglobin suggests this known SCA modifier may have a therapeutic role in modulating central sensitization.

Current Results and Future Research Priorities in Late Effects after Hematopoietic Stem Cell Transplantation for Children with Sickle Cell Disease and Thalassemia: A Consensus Statement from the Second Pediatric Blood and Marrow Transplant Consortium International Conference on Late Effects after Pediatric Hematopoietic Stem Cell Transplantation

Sustained donor engraftment after allogeneic hematopoietic cell transplantation (HCT) converts to healthy donor hemoglobin synthesis and halts disease symptoms in patients with sickle cell disease and thalassemia major. A disease-free survival probability that exceeds 90% has been reported when HCT using an HLA-matched sibling donor is performed in young patients with low-risk disease or treatment-related risk factors. Alternate donor HCT and HCT in adults is performed infrequently because of a higher risk profile. Transplant-specific risks include conditioning regimen-related toxicity, graft-versus-host disease, graft rejection with marrow aplasia or disease recurrence, and infections associated with immunosuppression and delayed immune reconstitution. The magnitude of risk depends on patient age, clinical status of the underlying disease (eg, organ injury from vasculopathy and iron overload), donor source, and intensity of the conditioning regimen. These risks are commonly monitored and reported in the short term. Documenting very late outcomes is important, but these data are rarely reported because of challenges imposed by patient drop-out and insufficient resources. This report summarizes long-term follow-up results after HCT for hemoglobin disorders, identifies gaps in knowledge, and discusses opportunities for future investigations. This consensus summary will be followed by a second article detailing comprehensive long-term follow-up recommendations to aid in maintaining health in these individuals and identifying late complication risks that could facilitate interventions to improve outcomes.

Disease-Related, Nondisease-Related, and Situational Catastrophizing in Sickle Cell Disease and Its Relationship With Pain

Catastrophizing is a potent psychological modulator of pain across several chronic pain populations; yet despite evidence that patients with sickle cell disease (SCD) catastrophize more than patients with other chronic pain conditions, previous research indicates that catastrophizing is not related to sickle cell pain after controlling for relevant covariates such as depression. Recent research suggests that pain-related catastrophizing should be assessed across pain contexts (eg, dispositional and situational). In this study, we measured disease-specific, general non-disease-related, and situational catastrophizing and assessed the relationship between these contextual dimensions of catastrophizing and laboratory and clinical pain among patients with SCD. Results revealed differential catastrophizing across pain contexts, with patients reporting greater catastrophizing about SCD-specific pain compared with non-SCD pain and laboratory pain. SCD-specific and non-SCD catastrophizing were associated with clinical pain outcomes, and situational catastrophizing with markers of central sensitization and laboratory pain. Further examination of the time course of laboratory responses revealed that increases in situational catastrophizing were associated with subsequent increases in laboratory pain sensitivity. Taken together, results show the relevance of catastrophizing in understanding pain in SCD, and suggest that context-specific anchors may be beneficial in predicting different aspects of the pain experience (eg, chronic pain, pain sensitization).

PERSPECTIVE

Patients with SCD report greater catastrophizing about sickle cell-specific pain relative to other pains. Disease-specific and non-disease-related pain catastrophizing were associated with clinical pain, and situational catastrophizing predictive of subsequent laboratory pain. Evaluation of context-specific catastrophizing may more accurately predict different aspects of the pain experience.

Comparative Analysis of Pain Behaviours in Humanized Mouse Models of Sickle Cell Anemia

Pain is a hallmark feature of sickle cell anemia (SCA) but management of chronic as well as acute pain remains a major challenge. Mouse models of SCA are essential to examine the mechanisms of pain and develop novel therapeutics. To facilitate this effort, we compared humanized homozygous BERK and Townes sickle mice for the effect of gender and age on pain behaviors. Similar to previously characterized BERK sickle mice, Townes sickle mice show more mechanical, thermal, and deep tissue hyperalgesia with increasing age. Female Townes sickle mice demonstrate more hyperalgesia compared to males similar to that reported for BERK mice and patients with SCA. Mechanical, thermal and deep tissue hyperalgesia increased further after hypoxia/reoxygenation (H/R) treatment in Townes sickle mice. Together, these data show BERK sickle mice exhibit a significantly greater degree of hyperalgesia for all behavioral measures as compared to gender- and age-matched Townes sickle mice. However, the genetically distinct "knock-in" strategy of human α and β transgene insertion in Townes mice as compared to BERK mice, may provide relative advantage for further genetic manipulations to examine specific mechanisms of pain.

Pharmacologic Treatment of Pain

Adolescents and children are frequently affected by chronic pain conditions that can lead to disability and distress. The best approach to evaluation and treatment of these conditions involves use of the biopsychosocial model, which includes use of medication management. Chronic pain conditions are treated pharmacologically with a number of different medication classes via several routes of administration as drug delivery systems have progressed. These include anti-inflammatory drugs, muscle relaxants, antiepileptic medicines, antidepressants, opioids, and local anesthetics. Most are prescribed without regulatory body approval to treat specific pain syndromes as data to support their use are sparse. Medical decision making is guided by experience, empiric evidence, extrapolation from adult studies, and matching medication classes with the theorized mechanism of the pain condition. It is not recommended that nonpain practitioners prescribe opioid medications for treatment of chronic pain conditions, and pain management practitioners should seek to minimize their use. The appropriate and commonly used medications for pain conditions are presented in this narrative review.