Trajectories of acute low back pain: latent class growth analysis

Background: Most people will recover from acute non-specific low back pain, but some do not. There is a paucity of longitudinal evidence describing how many individuals do not recover from acute low back pain. Understanding the course of acute low back pain is important to establish how many patients may need early intervention. This part of our study aimed to identify pain trajectories in patients presenting to primary care for acute low back pain. Methods: Participants were adults consulting general practice with acute low back pain, recruited for a placebo controlled trial of paracetamol. Pain numerical rating scale data (score range 0-10) was collected at baseline, weeks 1, 2, 4 and 12. Latent Class Growth Analysis (LCGA) was used to identify pain trajectories, based on trichotomised pain scores (0 = no pain, 1 – 4 = moderate pain, ≥ 5 = high pain). Results: In total, 1,505 participants who provided at least four pain scores (i.e. at four out of the five collection points) were analyzed. Six distinct clusters were identified including : ‘delayed pain recovery’(n = 529), ‘incomplete pain recovery’ (n = 378), ‘early pain recovery’ (n = 371), ’fluctuating recurrent pain’ (n = 115), ‘persistent high pain’(n = 83) and ‘fluctuating pain with recovery’ (n = 29). Conclusions: Overall, 38% of primary care attendees with acute low back pain show early tendency for pain persistence, recurrence or partial recovery. Describing baseline characteristics associated with the trajectories and conducting a long-term follow-up will help to identify patients in need of early intervention.