No evidence of convergent validity between the Fremantle back awareness questionnaire and tactile spatial processing measures in chronic low back pain

Background Chronic low back pain (CLBP) is associated with altered perception of the back. The Fremantle Back Awareness Questionnaire (FreBAQ) measures subjective back-specific body perception disturbance (BPD), which is consistently elevated in CLBP. Two-point discrimination (TPD) and two-point estimation (TPE) are psychophysical measures of tactile spatial processing. Whether FreBAQ converges with these measures remains incompletely understood. While the FreBAQ consistently showed no detectable association with TPD in prior studies, no study has specifically examined FreBAQ-TPE associations. TPE, which is thought to depend more strongly than TPD on an internal model of body size and shape, was hypothesised to align more closely with the FreBAQ. This study evaluated evidence for FreBAQ convergent validity against TPD and TPE in adults with CLBP and quantified stimulus orientation effects. Methods Cross-sectional study, n = 35 adults with non-specific CLBP. TPD and TPE were assessed bilaterally in horizontal and vertical orientations. Convergent validity was evaluated via Spearman correlations and Bayes factors (BF01). Results FreBAQ showed no significant correlation with TPD (ρ = 0.157, p = .367, BF01 = 3.22) or TPE error (ρ = −0.125, p = .475, BF01 = 3.72). Significant orientation effects (p’s < 0.001) were observed for both TPD (t(34) = 15.44, dz = 2.61) and TPE (t(34) = 4.75, dz = 0.80). Neither age, pain intensity, nor pain duration was significantly associated with tactile spatial measures. Conclusions Consistent with prior work, no evidence supporting convergent validity between the FreBAQ and TPD was found. Contrary to our hypothesis, no detectable association was found between the FreBAQ and TPE. Overall, the findings did not support convergent validity in this sample and suggest that the FreBAQ and the two tactile measures may capture different aspects of body perception. Trial registration ClinicalTrials.gov, NCT04869514 (parent trial). Registered 28 April 2021.