Prediction of Pain Outcomes in a Randomized Controlled Trial of Dose-response of Spinal Manipulation for the Care of Chronic Low Back Pain
SOURCE: BMC Musculoskelet Disord. 2015 (Aug 19); 16: 205 ~ FULL TEXT
Darcy Vavrek, Mitchell Haas,
Moni Blazej Neradilek, and Nayak Polissar
University of Western States,
2900 NE 132nd Ave,
Portland, OR, 97230, USA
BACKGROUND: No previous studies have created and validated prediction models for outcomes in patients receiving spinal manipulation for care of chronic low back pain (cLBP). We therefore conducted a secondary analysis alongside a dose-response, randomized controlled trial of spinal manipulation.
METHODS: We investigated dose, pain and disability, sociodemographics, general health, psychosocial measures, and objective exam findings as potential predictors of pain outcomes utilizing 400 participants from a randomized controlled trial. Participants received 18 sessions of treatment over 6-weeks and were followed for a year. Spinal manipulation was performed by a chiropractor at 0, 6, 12, or 18 visits (dose), with a light-massage control at all remaining visits. Pain intensity was evaluated with the modified von Korff pain scale (0-100). Predictor variables evaluated came from several domains: condition-specific pain and disability, sociodemographics, general health status, psychosocial, and objective physical measures. Three-quarters of cases (training-set) were used to develop 4 longitudinal models with forward selection to predict individual “responders” (≥50% improvement from baseline) and future pain intensity using either pretreatment characteristics or post-treatment variables collected shortly after completion of care. The internal validity of the predictor models were then evaluated on the remaining 25% of cases (test-set) using area under the receiver operating curve (AUC), R(2), and root mean squared error (RMSE).
RESULTS: The pretreatment responder model performed no better than chance in identifying participants who became responders (AUC = 0.479). Similarly, the pretreatment pain intensity model predicted future pain intensity poorly with low proportion of variance explained (R(2) = .065). The post-treatment predictor models performed better with AUC = 0.665 for the responder model and R(2) = 0.261 for the future pain model. Post-treatment pain alone actually predicted future pain better than the full post-treatment predictor model (R(2) = 0.350). The prediction errors (RMSE) were large (19.4 and 17.5 for the pre- and post-treatment predictor models, respectively).
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CONCLUSIONS:   Internal validation of prediction models showed that participant characteristics preceding the start of care were poor predictors of at least 50% improvement and the individual’s future pain intensity. Pain collected shortly after completion of 6 weeks of study intervention predicted future pain the best.
From the FULL TEXT Article:
The most common cause of disability is low back pain with an estimated 1099 years of life lost to disability each year per 100,000 people, worldwide, in 2010 . The prevalence of chronic low back pain (cLBP) is approximately 10 % [1, 2]. An effective approach to treating low back pain can include spinal manipulative therapy (SMT) [3–5]. Advantageously, treatment of cLBP with spinal manipulative therapy does not appear to increase the cost of treatment plus lost productivity . The question remains though, about what kind of patient has a greater chance of benefit with efficacious conservative therapies such as SMT [7–9], mechanical lumbar traction , and a stabilization exercise program . Our study is a step in this direction and to our knowledge, this is the only study to date that has sought to create prediction models of prognosis in individuals receiving a dose of SMT for the care of cLBP. This scientific inquiry is of great societal interest given today’s environment of prevention of opiate deaths in chronic pain management [12–16].