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Objectives: To examine acceptability of study participation and feasibility of (1) recruitment, (2) data collection and (3) outcome measures for the prospective U-PAIN cohort. Design: Internal feasibility study of a prospective cohort. Participants and setting: 64 patients, >18 years, with chronic pain at a multidisciplinary pain centre at a university hospital in Sweden. Outcome measures: Acceptability of study participation was measured with a study-specific 10-item Likert scale. A score <3 was considered feasible, for the two items that assessed respondent burden a higher score indicated lesser participant burden and a score >3 was feasible. Recruitment was assessed by participation rates at baseline and retention at the 1-year follow-up, with threshold values for feasibility at 75% and 80%, respectively. Data collection and outcome measures were examined by completions rates of study procedures (90% was considered feasible), sample scores, internal consistency (alpha>0.70 was considered feasible), and agreement between self-reported data and data retrieved from medical records on opioid use (ICC or kappa>0.60 was considered feasible). Results: Acceptability for study procedures was feasible, but participation rates were low: 25%. The retention rate at 1-year follow-up was 81% for those included in the feasibility study, that is, filling out computerised patient-reported outcome measures, and 65% for those using paper and pencil format. The completion rates for the different data collection methods ranged from 83% to 95%. Agreement between self-reported opioid use and prescribed dose and between opioid use disorder according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5), and clinical International Classification of Diseases-10 (ICD-10) diagnoses for opioid dependence were almost perfect (kappa=0.91and kappa=0.90, respectively). Conclusions: This feasibility study has helped to explore and improve methods for recrui

Anne-Li Lind,1 David Just,2 Maria Mikus,2 Claudia Fredolini,2 Marina Ioannou,2 Björn Gerdle,3 Bijar Ghafouri,3 Emmanuel Bäckryd,3 Lars Tanum,4 Torsten Gordh,1 Anna Månberg2 1Department of Surgical Sciences, Uppsala University, Uppsala, Sweden; 2Division of Affinity Proteomics, SciLifeLab, Deptartment of Protein Science, KTH Royal Institute of Technology, Stockholm, Sweden; 3Pain and Rehabilitation Center, and Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; 4Department of R&D in Mental Health, Akershus University Hospital, Lørenskog, NorwayCorrespondence: Anna MånbergDivision of Affinity Proteomics, SciLifeLab, Department of Protein Science, KTH - Royal Institute of Technology, Tomtebodvägen 23A, Solna, Stockholm, SwedenTel +46 8 790 9803Email anna.manberg@scilifelab.seObjective: Neuropathic pain and fibromyalgia are two common and poorly understood chronic pain conditions that lack satisfactory treatments, cause substantial suffering and societal costs. Today, there are no biological markers on which to base chronic pain diagnoses, treatment choices or to understand the pathophysiology of pain for the individual patient. This study aimed to investigate cerebrospinal fluid (CSF) protein profiles potentially associated with fibromyalgia and neuropathic pain.Methods: CSF samples were collected from 25 patients with neuropathic pain (two independent sets, n=14 patients for discovery, and n=11 for verification), 40 patients with fibromyalgia and 134 controls without neurological disease from two different populations. CSF protein profiling of 55 proteins was performed using antibody suspension bead array technology.Results: We found increased levels of apolipoprotein C1 (APOC1) in CSF of neuropathic pain patients compared to controls and there was a trend for increased levels also in fibromyalgia patients. In addition, levels of ectonucleotide

In addition to central hyperexcitability and impaired top-down modulation, chronic inflammation probably plays a role in the pathophysiology of fibromyalgia (FM). Indeed, on the basis of both animal experiments and human studies involving the analysis of cytokines and other inflammation-related proteins in different body fluids, neuroinflammatory mechanisms are considered to be central to the pathophysiology of many chronic pain conditions. However, concerning FM, previous human plasma/serum and/or cerebrospinal fluid (CSF) cytokine studies have looked only at a few predetermined cytokine candidates. Instead of analyzing only a few substances at a time, we used a new multiplex protein panel enabling simultaneous analysis of 92 inflammation-related proteins. Hence, we investigated the CSF and plasma inflammatory profiles of 40 FM patients compared with CSF from healthy controls (n= 10) and plasma from blood donor controls (n= 46). Using multivariate data analysis by projection, we found evidence of both neuroinflammation (as assessed in CSF) and chronic systemic inflammation (as assessed in plasma). Two groups of proteins (one for CSF and one for plasma) highly discriminating between patients and controls are presented. Notably, we found high levels of CSF chemokine CX3CL1 (also known as fractalkine). In addition, previous findings concerning IL-8 in FM were replicated, in both CSF and plasma. This is the first time that such an extensive inflammatory profile has been described for FM patients. Hence, FM seems to be characterized by objective biochemical alterations, and the lingering characterization of its mechanisms as essentially idiopathic or even psychogenic should be seen as definitively outdated., Funding Agencies|Uppsala Berzelii Technology Centre for Neurodiagnostics; Swedish Governmental Agency for Innovation Systems (Vinnova); Swedish Research Council [P29797-1]

Emmanuel Bäckryd,1,* Lars Tanum,2,* Anne-Li Lind,3 Anders Larsson,4 Torsten Gordh,3 1Pain and Rehabilitation Center, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden; 2Department of R&D in Mental Health, Akershus University Hospital, Lørenskog, Norway; 3Department of Surgical Sciences, 4Department of Medical Sciences, Uppsala University, Uppsala, Sweden *These authors contributed equally to this work Abstract: In addition to central hyperexcitability and impaired top–down modulation, chronic inflammation probably plays a role in the pathophysiology of fibromyalgia (FM). Indeed, on the basis of both animal experiments and human studies involving the analysis of cytokines and other inflammation-related proteins in different body fluids, neuroinflammatory mechanisms are considered to be central to the pathophysiology of many chronic pain conditions. However, concerning FM, previous human plasma/serum and/or cerebrospinal fluid (CSF) cytokine studies have looked only at a few predetermined cytokine candidates. Instead of analyzing only a few substances at a time, we used a new multiplex protein panel enabling simultaneous analysis of 92 inflammation-related proteins. Hence, we investigated the CSF and plasma inflammatory profiles of 40 FM patients compared with CSF from healthy controls (n=10) and plasma from blood donor controls (n=46). Using multivariate data analysis by projection, we found evidence of both neuroinflammation (as assessed in CSF) and chronic systemic inflammation (as assessed in plasma). Two groups of proteins (one for CSF and one for plasma) highly discriminating between patients and controls are presented. Notably, we found high levels of CSF chemokine CX3CL1 (also known as fractalkine). In addition, previous findings concerning IL-8 in FM were replicated, in both CSF and plasma. This is the first time that such an extensive inflammatory profile has been descri

Earlier studies suggest that lumbar radicular pain following disc herniation may be associated with a local or systemic inflammatory process. In the present study, we investigated the serum inflammatory protein profile of such patients. All 45 patients were recruited from Oslo University Hospital, Ulleval, Norway, during the period 2007-2009. The new multiplex proximity extension assay (PEA) technology was used to analyze the levels of 92 proteins. Interestingly, the present data showed that patients with radicular pain 12 months after disc herniation may be different from other patients with regard to many measurable serum cytokines. Given a false discovery rate (FDR) of 0.10 and 0.05, we identified 41 and 13 proteins, respectively, which were significantly upregulated in the patients with severe pain one year after disc herniation. On the top of the list ranked by estimated increase we found C-X-C motif chemokine 5 (CXCM5; 217% increase), epidermal growth factor (EGF; 142% increase), and monocyte chemotactic protein 4 (MCP-4; 70% increase). Moreover, a clear overall difference in the serum cytokine profile between the chronic and the recovered patients was demonstrated. Thus, the present results may be important for future protein serum profiling of lumbar radicular pain patients with regard to prognosis and choice of treatment. We conclude that serum proteins may be measurable molecular markers of persistent pain after disc herniation.

The objective of this study was to develop and apply a novel multiplex panel of solid-phase proximity ligation assays (SP-PLA) requiring only 20 μL of samples, as a tool for discovering protein biomarkers for neurological disease and treatment thereof in cerebrospinal fluid (CSF). We applied the SP-PLA to samples from two sets of patients with poorly understood nervous system pathologies amyotrophic lateral sclerosis (ALS) and neuropathic pain, where patients were treated with spinal cord stimulation (SCS). Forty-seven inflammatory and neurotrophic proteins were measured in samples from 20 ALS patients and 15 neuropathic pain patients, and compared to normal concentrations in CSF from control individuals. Nineteen of the 47 proteins were detectable in more than 95% of the 72 controls. None of the 21 proteins detectable in CSF from neuropathic pain patients were significantly altered by SCS. The levels of the three proteins, follistatin, interleukin-1 alpha, and kallikrein-5 were all significantly reduced in the ALS group compared to age-matched controls. These results demonstrate the utility of purpose designed multiplex SP-PLA panels in CSF biomarker research for understanding neuropathological and neurotherapeutic mechanisms. The protein changes found in the CSF of ALS patients may be of diagnostic interest.

Aims: Cathepsin S has been reported to be a biomarker of spinal microglial activation, a process suggested to be involved in the pathophysiology of chronic neuropathic pain. So far this has been shown only in animal experiments. The aim of this study was to investigate the concentrations of cathepsin S in human cerebrospinal fluid (CSF) samples from a well-defined patient cohort suffering from neuropathic pain as compared to controls. Methods: CSF samples from patients suffering from chronic neuropathic pain (n = 14) were analyzed for cathepsin S levels using commercial sandwich ELISAs (DY1183, R&D Systems, Minneapolis, MN, USA). Control CSF was sampled from patients undergoing minor urological surgical procedures under spinal anaesthesia (n = 70), having no obvious pain suffering. Results: The neuropathic pain group had significantly higher levels of CSF cathepsin S (median 15189 pg/mL, range 3213–40,040), than the control group (median 5911 pg/mL, range 1909–17,188) (p < 0.005, Mann–Whitney U-test). Conclusion: The results support the existence of microglial activation in chronic neuropathic pain patients. CSF Cathepsin S may serve as a potential biomarker for this specific mechanism linked to neuropathic pain. In the future, Cathepsin S inhibiting drugs might become a new treatment alternative for neurophatic pain.

Objectives: This study aimed to investigate the acceptability of study participation and feasibility of i) recruitment, ii) data collection and iii) outcome measures of a prospective cohort of patients with chronic-non-cancer pain (CNCP), the U-PAIN cohort. The overall aim of the cohort study is to identify predictors for risks and benefits associated with chronic opioid therapy (COT). Design: Internal feasibility study including baseline data and retention rate of the one-year follow-up. Setting: A secondary and tertiary care Pain Center at a university hospital in Sweden with a national catchment area. Participants: Sixty-four patients with CNCP, > 18 years, literate in Swedish, referred to consultation and/or treatment at the Pain Centre. Outcome measures: Acceptability of study participation was measured with a study-specific 10-item Likert scale. Feasibility of recruitment was assessed by recording participation rates at baseline and number of individuals completing the one-year follow-up. Feasibility of data collection and outcome measures in the cohort study were examined by completions rates of study procedures, sample scores, and agreement between self-reported data and data retrieved from medical records on opioid use. Results: Study participants reported an overall acceptable satisfaction with Participation retention rate at the one-year follow-up was 82%. The completion rates for the different data collection methods ranged from 83% to 95%. Agreement between self-reported opioid use and prescribed dose was high (к= .91). Eleven individuals met the criteria for any OUD, and three individuals met the criteria for moderate- severe OUD. Agreement between OUD according to DSM-5, and clinical ICD-10 diagnoses for opioid dependence measured with prevalence-adjusted and bias-adjusted kappa (PABAK) was high (κ= .90). The participants reported poor work ability. Conclusions: This feasibility study has helped to highlight and improve methods for re

Objective: Today, there are no biological tests on which to base pain diagnoses, treatment choices or to understand the biological processes underlying and accompanying chronic pain for the individual pain patient. Relevant biological markers would greatly aid in diagnosis and treatment of patients with chronic pain. Our study aimed to find proteins in CSF associated with fibromyalgia and neuropathic pain, two common and poorly understood chronic pain conditions. Methods: We have performed CSF protein profiling of 55 proteins using a 100-plex antibody suspension bead array. We collected, analyzed and compared CSF samples from 25 patients with neuropathic pain (two independent sets, n=14 patients for discovery and n=11 for verification), 40 patients with fibromyalgia and 135 controls without neurological disease from two different populations. Results: We found significant differences in CSF protein levels between patients and controls (p<0.05). Among these proteins, Apolipoprotein C1 (APOC1) was found to be increased in CSF of neuropathic pain patients compared to controls and there was a non-significant trend for increased levels also in fibromyalgia patient CSF. Ectonucleotide pyrophosphatase (ENPP2, Autotaxin) was increased in the CSF of fibromyalgia patients compared to all other groups including neuropathic pain patients. Multivariate analysis revealed partially overlapping and partially distinct CSF profiles in neuropathic pain patients compared with fibromyalgia and controls for several other proteins including angiotensinogen (AGT), prostaglandin-H2 D-isomerase (PTGDS), neurexin-1 (NRXN1), superoxide dismutase 1 (SOD1) and superoxide dismutase 3 (SOD3). Conclusions: Our results, suggest that the CSF protein profiles of neuropathic pain and fibromyalgia patients may be different from each other and from those of controls. CSF levels of APOC1, ENPP2, AGT, PTGDS, NRXN1, SOD1 and SOD3 should be further investigated for their potential to serve as biomarkers, Berzelii Technology Centre of Neurodiagnostics

Spinal cord stimulation (SCS) is a widely used mode of therapy in neuropathic pain of peripheral origin. Despite its well-established clinical use, the underlying physiological mechanisms behind the beneficial analgesic effects of SCS still remain only partially known. In this study, a proteomic approach was used to compare the protein concentration in cerebrospinal fluid (CSF) from responsive human patients (n=12). The comparison was made between samples taken during at two different timepoints. The first sample was taken when the stimulator had been off for 48 h, the second sample was taken after the stimulator had been used for three weeks. In total, 419 proteins could be identified (P<0.05) and relatively quantified using a shotgun proteomic approach based on immunoaffinity fractionation, multiplexed dimethyl labeling and reversed phase nanoliquid chromatography in combination with electrospray ionization high resolution tandem mass spectrometry. Statistical analysis (P<0.01) revealed two significantly down-regulated proteins; Co2 (P=0.0046), Ibp6 (P=0.0071) and five up-regulated proteins; Lynx1 (P=0.000048), Klk6 (P=0.00058), Angt (P=0.00057), A4 (P=0.0052) and Sap3 (P=0.0076) during the on state. Lynx1was the most significantly and consistently increased protein in all patients. Lynx1 is a modulator of the nicotinic acetylcholine receptor activity in the central nervous system previously described in mice. This study reports for the first time the possible involvement of Lynx1 in SCS-induced analgesia in humans.