Back pain "red flags": which are most predictive of serious pathology in the Emergency Department?

To determine the frequency of red flag signs and symptoms in patients presenting with back pain to the Emergency Department (ED) and association with serious pathologies and investigations performed.

This retrospective observational study evaluated consecutive patients presenting with back pain to a Melbourne ED over a 14-month period. Data regarding red flags, patient characteristics, ED-initiated investigations, and diagnoses were extracted from medical records. Prevalence of each red flag and sensitivity, specificity, and likelihood ratios for diagnosing serious spinal or non-spinal pathology were calculated.

Analysis was undertaken on 1000 eligible participants with back pain. 69% had red flags. Participants were categorised into diagnostic groups: musculoskeletal (80.6%), serious spinal (3.3%), and serious non-spinal (14.6%) pathologies. A number of red flags had positive likelihood ratios (LR) > 5, indicating a higher probability of serious pathology (spinal/non-spinal) including fever (LR + 68.8), tuberculosis history (LR + 13.8), known nephrolithiasis/abdominal aortic aneurysm (LR + 10.2), unexplained weight-loss (LR + 9.2), writhing in pain (LR + 6.9), urinary symptoms (LR + 5.4), and flank pain (LR + 5.2). Red flags with positive LR > 5 indicating a higher probability of serious spinal pathology were saddle anaesthesia (LR + 11.0), tuberculosis history (LR + 9.8), intravenous drug-use (LR + 6.9), acute-onset urinary retention (LR + 6.4), and anal tone loss (LR + 6.3).

The majority of this study cohort had back pain of benign cause. Some red flags were associated with greater risk of serious pathology, others were not. Further evidence regarding red flags and their association with serious pathology is required, to better inform clinical guidelines.