A pilot study in the association between Waddell Non-organic Signs and Central Sensitization

Study design: A cross-sectional observational multicenter pilot-study was performed within care as usual in three rehabilitation centers in the Netherlands.

Objective: To explore the relationship between Waddell Non-organic Signs (NOS) and Central Sensitization (CS) in patients with chronic back pain.

Summary of background data: A possible relationship between NOS and CS is theoretically plausible, but it has never been tested.

Methods: A cross-sectional observational multicenter pilot-study was performed in three rehabilitation centers in the Netherlands. Patients with chronic back pain were included. Main measures were Waddell's NOS, a battery of eight clinical tests performed during a physical examination, and Central Sensitization Inventory (CSI), a questionnaire measuring symptoms originating from CS. Analyses included Spearman correlation and univariate multiple regression analysis with NOS as dependent variable, CSI as independent, and controlled for confounders (psychosocial variables).

Results: Data of n = 56 patients (59% female, mean age 42.6 years) were obtained. Correlation between NOS and CSI was rs = 0.34 (p = 0.01). After controlling for confounders, CSI did not independently predict NOS.

Conclusion: In this pilot study, CS was moderately related to NOS, but CS did not independently contribute to NOS after controlling for confounders. The results suggest that NOS may not exclusively be non-organic tests, although questions remain. The results of this pilot study can help to develop larger studies to allow replication and more detailed analyses.