Determining One-Year Trajectories of Low-Back-Related Leg Pain in Primary Care Patients: Growth Mixture Modeling of a Prospective Cohort Study.

Reuben O Ogollah,Kika Konstantinou,Siobhán Stynes,Kate M Dunn

doi:10.1002/acr.23556

Abstract

The clinical presentation and outcome of patients with back and leg pain in primary care are heterogeneous and may be better understood by identification of homogeneous and clinically meaningful subgroups. Subgroups of patients with different back pain trajectories have been identified, but little is known about the trajectories for patients with back-related leg pain. This study sought to identify distinct leg pain trajectories, and baseline characteristics associated with membership of each group, in primary care patients. Monthly data on leg pain intensity were collected over 12 months for 609 patients participating in a prospective cohort study of adult patients seeking health care for low-back and leg pain, including sciatica, of any duration and severity, from their general practitioner.Growth mixture modeling was used to identify clusters of patients with distinct leg pain trajectories. Trajectories were characterized using baseline demographic and clinical examination data. Multinomial logistic regression was used to predict latent class membership, with a range of covariates. Four patient clusters were identified: improving mild pain (58%), persistent moderate pain (26%), persistent severe pain (13%), and improving severe pain (3%). Clusters showed statistically significant differences in a number of baseline characteristics. Four trajectories of leg pain were identified. Clusters 1, 2, and 3 were generally comparable to back pain trajectories, while cluster 4, with major improvement in pain, is infrequently identified. Awareness of such distinct patient groups improves understanding of the course of leg pain and may provide a basis of classification for intervention.

Highlights

Low back pain (LBP) is a common condition and a major cause of disability globally[1] and results in an immense economic burden[2]
Monthly data on leg pain intensity were collected over 12 months for 609 patients participating in a prospective cohort study of adult patients seeking healthcare for low back and leg pain including sciatica, of any duration and severity, from their general practitioner
The “improving severe” cluster represented a group with severe leg pain, whose symptoms improved over time– this group is less often identified in back pain patients

Summary

Introduction

Low back pain (LBP) is a common condition and a major cause of disability globally[1] and results in an immense economic burden[2]. Studies on the clinical course of most musculoskeletal pain conditions[6,7,8,9] have mainly shown a marked improvement in pain within the first few weeks, but after that point improvement slows considerably These findings are based on single growth trajectories with the assumption that individuals are drawn from a single homogeneous population with common population parameters. The moderate to high person-to-person variability in pain at follow-up time points reported in these studies[7] clearly points to the heterogeneity in the clinical course of pain This has led to a number of studies in the past decade focussing on investigation of the underlying averaged course of LBP, and has demonstrated that different trajectory patterns exist[10, 11]

Methods

Results

Discussion

Conclusion