Background & Aims
Chronic pain conditions may be associated with a disruption of the cortical representation of the body within the somatosensory cortex [1], known as cortical disruption [2]. Cortical disruption may play a role in the development/maintenance of chronic pain. Patients with non-specific chronic low back pain (NSCLBP) can have cortical disruption [3, 4], presenting clinically as impaired sensorimotor function. Direct measurement of cortical representation is expensive and requires hi-tech equipment [5]. Thus, simple sensorimotor clinical tests such as graphesthesia are often used as proxy measures [5], as both constructs are related [6-9]. Graphesthesia is defined as ‘the ability to recognise, symbols written on the skin’ [10]. This study aimed to quantify the intra- and inter-tester reliability of graphesthesia in people with NSCLBP and provide initial values for a minimally clinically important difference(MCID).
Methods
Twelve men and twenty-three women with NSCLBP were recruited (mean±SD age: 52±15 years). Participants assumed a prone position. The graphesthesia assessment protocol was adapted from the protocol by Wand et al [11] . Three clinicians drew 60 letters with the blunt end of a knitting needle (approximate diameter 2 mm) over the area of most pain at the lower back during two consecutive sessions. One of these clinicians repeated the assessment protocol within 7 days. An error rate out of 60 was calculated for each participant. The lower the error rate the better the score. Intra- and inter-tester reliability was quantified using mean difference, within-subject SD and limits of agreement (LOA). The MCID was defined as 0.5SD of baseline values for tester 1 for session 1 [12]. The within subjects SD (standard error of measurement [SEM]) and MCID was used to estimate the sample size required for future trials attempting to detect the MCID.
Results
Regarding intra-tester reliability, the mean value for graphesthesia scores obtained from the participants by assessor 1 on session 1 was 42% (out of 60 letters) and 36% on session 2 (mean difference 5.3 % [95 % CI: 1.89 to 8.68]). The ICC3.1 value for absolute agreement was 0.84 (95 %CI: 0.65 to 0.93). Regarding inter-tester reliability for tester 1 and 2 participants had an error rate of 42 % for tester 1 and 39 % for test-er 2 (mean session difference 3.6 % [95 % CI: -0.56 to 6.73]). The ICC3.1 values for absolute agreement were 0.58 (95 %CI: 0.72 to 0.92). Using an MCID of 10% it can be estimated that n=10 would be required for a future single arm pre-post study (two-tailed p<0.05, power = 90%) and n=34 (17 per arm) for a future two-arm randomised controlled trial. The SEM was 7%. However, with 19% LOA, illustrating that individual normal variation was large.
Conclusions
The current graphesthesia protocol demonstrated acceptable systematic and random error values for future research purposes. However, the magnitude of the LOA com-pared to the formally estimated MCID indicate a large amount of random variability, questioning the current applicability for an individual patient measurement in a clinical setting. Future studies should aim to formally establish longitudinal anchor-based MCIDs for this construct.
References
1.May, A., Chronic pain may change the structure of the brain. Pain, 2008. 137(1): p. 7-15.
2.Bowering, K.J., et al., Motor imagery in people with a history of back pain, current back pain, both, or neither. Clinical Journal of Pain, 2014. 30(12): p. 1070-1075.
3.Haggard, P., G.D. Iannetti, and M.R. Longo, Spatial sensory organization and body representation in pain perception. Curr Biol, 2013. 23(4): p. R164-76.
4.Viceconti, A., et al., Explicit and Implicit Own’s Body and Space Perception in Painful Musculoskeletal Disorders and Rheumatic Diseases: A Systematic Scoping Review. Frontiers in Neuroscience, 2020. 14: p. 83.
5.Lloyd, D., et al., Differences in Low Back Pain Behavior Are Reflected in the Cerebral Response to Tactile Stimulation of the Lower Back. Spine (Philadelphia, Pa.1976), 2006. 33(12): p. 1372-1377.
6.Garcia-Larrea, L. and F. Mauguière, Pain syndromes and the parietal lobe. Handb Clin Neurol, 2018. 151: p. 207-223.
7.Mørch, C.D., et al., Exteroceptive aspects of nociception: insights from graphesthesia and two-point discrimination. Pain, 2010. 151(1): p. 45-52.
8.Harvie, D.S., et al., When touch predicts pain: predictive tactile cues modulate perceived intensity of painful stimulation independent of expectancy. Scand J Pain, 2016. 11: p. 11-18.
9.Harvie, D.S., G. Edmond-Hank, and A.D. Smith, Tactile acuity is reduced in people with chronic neck pain. Musculoskelet Sci Pract, 2018. 33: p. 61-66.
10.Drago, V., et al., Graphesthesia: A test of graphemic movement representations or tactile imagery? Journal of the International Neuropsychological Society, 2010. 16(01): p. 190-193.
11.Wand, B.M., et al., Managing Chronic Nonspecific Low Back Pain With a Sensorimotor Retraining Approach: An Exploratory Multiple-Baseline Study of 3 Participants. Physical Therapy, 2011.
12.Norman, G.R., J.A. Sloan, and K.W. Wyrwich, Interpretation of changes in health-related quality of life: the remarkable universality of half a standard deviation. Med Care, 2003. 41(5): p. 582-92.
Presenting Author
Katja Ehrenbrusthoff
Poster Authors
Katja Ehrenbrusthoff
PhD
Hochschule fuer Gesundheit Bochum
Lead Author
Topics
- Specific Pain Conditions/Pain in Specific Populations: Low Back Pain