Georgopoulos, Vasileios
(2020)
Central sensitisation as a predictor of self-management in chronic low back pain.
PhD thesis, University of Nottingham.
Abstract
Background: Chronic low back pain (CLBP) is one of the most prevalent reasons people seek healthcare assistance worldwide. Guidelines for managing CLBP prioritise the development of self-management strategies. Levels of central sensitisation (CS) may contribute to the relatively poor efficacy of treatments aiming to facilitate self-management. CS might be a dominant factor predicting worse self-management in people with CLBP following interventions aiming to improve such outcomes. Quantitative sensory testing (QST) may provide reliable and valid indices of CS and it may predict musculoskeletal pain and disability. CS might be associated with increasing psychological distress, pain, fatigue and catastrophisation which might also be predictors of ineffective self-management. CS has also been associated in people with knee pain with self-report measures of widespread pain distribution (reported by shading a pain manikin) or a self-report Central Mechanisms Trait score, comprising of items addressing depression, anxiety, neuropathic-like symptoms, pain distribution, catastrophising, sleep, fatigue and cognitive difficulties.
Objectives: [1] to systematically review the literature in order to determine the ability of QST to predict musculoskeletal outcomes; [2] to establish the reliability and validity of distinct QST modalities as classification and measurement tools of CS; [3] to establish a cut off for number of body sites shaded on a self-reported pain manikin that best identifies those with widespread pain and explore whether certain self-reported items taken to indicate central mechanisms involvement contribute to a single latent trait in individuals with CLBP; [4] to determine whether different CS indices are associated specifically with self-management/self-care outcomes at a single time-point; [5] to test whether any cross-sectional associations between baseline CS indices and self-management/self-care outcomes are also present longitudinally, after participants have undertaken an intervention programme that aimed to improve such outcomes.
Methods: A systematic literature review (SLR) was conducted to collate the evidence regarding the ability of QST to predict pain, disability and negative affect using searches of 6 databases up to April 2018. Title screening, data extraction, and methodological quality assessments were performed independently by 2 reviewers. Associations were reported between baseline QST and outcomes using adjusted (β) and unadjusted (r) correlations.
Reliability of Pressure Pain Detection Threshold (PPT), Temporal Summation (TS) and Conditioned Pain Modulation (CPM) conducted at a site distant from the low back were assessed in healthy participants (n=25) and individuals with CLBP (n=25). The QST test site was the dominant forearm and conditioning site the contralateral arm.
Pain distribution was classified according to criteria proposed by the American College of Rheumatology (ACR) and other research groups. Receiver operating characteristics (ROC) analysis established the cut-off point for the optimal number of painful sites needed to classify low PPT (1st quartile). Confirmatory factor analysis (CFA) was used to assess model fit and produce a single Central Mechanisms Trait score based on unique items form 8 distinct self-reported tools.
The ability of baseline indices of CS (PPT, TS, CPM, number of painful sites on a manikin, and Central Mechanisms Trait score) to predict self-management outcomes at 3-months follow-up was assessed in individuals with CLBP (n=97) participating in a cognitive behavioural therapy (CBT)-based group physiotherapy intervention, which aimed to facilitate self-management. Self-management was measured in 8 discrete domains; health-directed behaviour, positive engagement in life, self-monitoring and insight, constructive attitudes and approaches, skill and technique acquisition, social integration and support, health services navigation and emotional distress. Pain (numerical rating scale), depression/anxiety (hospital anxiety-depression scale), fatigue (fatigue severity scale) and catastrophising (pain catastrophising scale) were also measured.
Results: The SLR identified 37 eligible studies (n=3860 participants). Meta-analysis revealed that baseline QST predicted musculoskeletal pain (mean r=0.31, 95%CI: 0.23 to 0.38, n=1057 participants) and disability (mean r=0.30, 95%CI: 0.19 to 0.40, n=290 participants). Baseline modalities quantifying central mechanisms such as TS and CPM were associated with follow-up pain (TS: mean r=0.37, 95%CI: 0.17 to 0.54; CPM: r=0.36, 95%CI: 0.20 to 0.50), and baseline mechanical threshold modalities were predictive of follow-up disability (mean r=0.25, 95%CI: 0.03 to 0.45).
Test-retest and inter-rater reliability were high for PPT and TS in both normal and CLBP populations (ICC=0.76 to 0.92) but low for CPM (ICC=0.43 and 0.46 respectively).
In people with CLBP (n=97), ROC analysis determined that >9/24 painful sites optimally predicted low PPT at the forearm (AUC=0.67, 95%CI: 0.55 to 0.80). The single-factor Central Mechanisms Trait model showed a good fit to the data (CFI=0.92, TLI=0.88; RMSEA=0.09; SRMR=0.07; x2(df)=34.19(20)).
Follow-up questionnaires were completed by 87 people with CLBP (67% female, mean age 65y). Low PPT, inefficient CPM, the ACR and >9/24 classification criteria and the Central Mechanisms trait predicted less positive engagement in life (r=-0.54 to 0.31, p<0.05), low PPT and inefficient CPM each predicted increased emotional distress (PPT: r=-0.21, p<0.05; CPM: r=-0.29, p=0.01), and low PPT predicted worse social integration and support (r=0.28, p<0.01) at 3 months. Baseline Central Mechanisms trait scores predicted worse performance in health directed behaviour, positive engagement in life, constructive attitudes and approaches, social integration and support and emotional distress at 3-months (r=-0.56 to 0.54, p<0.05).
In multivariate regression models exploring the relationship between baseline CS indices (QST modalities, widespread pain identification methods, Central Mechanisms trait) and self-management outcomes, adjusted for other variables (age, sex, depression, catastrophisation, pain and fatigue), low PPT, inefficient CPM and Central Mechanisms trait scores, remained significantly associated (p<0.05) with social integration and support, positive engagement in life and constructive attitudes and approaches at 3 months respectively.
Conclusion: QST can predict musculoskeletal outcomes across a range of musculoskeletal conditions and discrete pain hypersensitivity indices (PPT and TS) demonstrate high reliability as pain quantification tool. Baseline indices of high CS can predict reduced ability of individuals with CLBP to self-manage their condition 3 months after commencing a CBT-based group physiotherapy intervention. Self-management is a multidimensional concept and its influence by factors other than CS merits further research. Treatments which specifically target CS might help remove barriers to self-management in people with CLBP.
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