Preliminary Validation of a Two-Point Estimation Task for the Measurement of Sensory Dissociation in Patients with Chronic Low Back Pain

Abstract

Objectives: Sensory dissociation (SEDI), the discrepancy between perception and actual size or shape of a painful body part, is a frequently observed finding in patients with chronic low back pain. However, the current methods of evaluating SEDI have several limitations, such as a qualitative nature and weak evidence supporting their reliability. In the current study, the reliability of two versions (manual and verbal) of a novel test, a two-point estimation task (TPE), was investigated.

Methods: To perform the manual version of the task, patients estimated the distance between two tactile stimuli delivered to their back using callipers, whereas in the verbal version they verbally reported the estimated distance.

Results: The manual version of TPE showed greater interexaminer reliability than the verbal version, and the mean of the two repeated measurements was sufficient for reaching excellent reliability for the pain-free (intraclass correlation coefficient [ICC] = 0.91, 95% confidence interval [CI] = 0.77-0.97) and painful (ICC = 0.86, 95% CI = 0.65-0.94) sides. Intra-examiner reliability was moderate to excellent (ICC = 0.66-0.96) for the manual version performed at the pain-free and painful sides. Distribution, duration, and intensity of pain significantly predicted SEDI and accounted for 42% of the total variance (corrected R2 = 0.42, P < 0.01).

Conclusions: TPE showed higher reliability coefficients compared with tools previously suggested in the literature and can therefore be used clinically and experimentally by one or more examiners. Further research is required to investigate the validity of this new test.

Keywords: Chronic Pain; Precision; Sensory Dissociation; Tactile Acuity; Two-Point Discrimination; Two-Point Estimation.