Pain and Disability in Low Back Pain can be Reduced despite No Significant Improvements in Mechanistic Pain Biomarkers

Objective: Altered balance in nociception in response to noxious stimuli is commonly reported in chronic low back pain (LBP). However, it is unclear whether an improvement in the clinical presentation is contingent on a reduction in pain sensitivity. This study investigated whether the quantitative sensory testing (QST) profile changes in people undergoing rehabilitation for LBP. Design: A prospective, observational case-control study. Methods: Forty males and females, 18-40 years' old, (20 with LBP) participated in two sessions. QST was performed at baseline and after discharge from rehabilitation (LBP) or after 3-8 weeks (controls). The QST battery consisted of determining pressure-pain thresholds (PPT) at the low back and shoulder, temporal summation of pain and conditioned pain modulation. Questionnaire data was used to determine pain (Numeric Rating Scale; NRS), disability (Roland-Morris Questionnaire, RMQ), Fear Avoidance Beliefs (FABQ) and The Örebro Musculoskeletal Pain Screening Questionnaire (ÖMPSQ) at baseline and discharge. The treatment effect was determined by calculating the Cohen's d. Results: No significant group x time interactions or main factor effect was found for any of the QST measures. The LBP group reported a significant reduction in NRS (P<0.0002, d=1.23), RMQ (P<0.0001, d=1.58), FABQ (P< 0.001, d=0.87) and in the ÖMPSQ (P<0.00001, d=1.44). Conclusions: The results indicate that an improvement of clinical LBP is not contingent upon changes in the pain sensory profile. The value of screening pain sensitivity in low back pain patients in primary care, needs to be investigated further, due to the patient population heterogeneity and the sensitivity of assessment methods.