Pressure Pain Threshold Testing Demonstrates Predictive Ability in People with Acute Whiplash

Study Design: Longitudinal cohort study.

Objectives: To determine whether pressure pain threshold (PPT), tested at 2 standardized sites, could provide additional prognostic ability to predict short-term outcomes in people with acute whiplash, after controlling for age, sex, and baseline pain intensity.

Background: PPT may be a valuable assessment and prognostic indicator for people with whiplash-associated disorder. The extent to which PPT can predict short-term disability scores has yet to be explored in people with acute (of less than 30 days in duration) whiplash-associated disorder in a clinical setting.

Methods: Eligible patients were recruited from community-based physiotherapy clinics in Canada. Baseline measurements included PPT, as well as pain intensity, age, and sex. Neck-related disability was collected with the Neck Disability Index 1 to 3 months after PPT testing. Multiple linear regression models were constructed to evaluate the unique contribution of PPT in the prediction of follow-up disability scores.

Results: A total of 45 subjects provided complete data. A regression model that included sex, baseline pain intensity, and PPT at the distal tibialis anterior site was the most parsimonious model for predicting short-term Neck Disability Index scores 1 to 3 months after PPT testing, explaining 38.6% of the variance in outcome. None of the other variables significantly improved the predictive power of the model.

Conclusion: Sex, pain intensity, and PPT measured at a site distal to the injury were the most parsimonious set of predictors of short-term neck-related disability score, and represented promising additions to assessment of traumatic neck pain. Neither age nor PPT at the local site was able to explain significant variance beyond those 3 predictors. Limitations to interpretation are addressed.