Do “red flags” signal serious pathology with low back pain?

When patients present to primary care physicians with acute low back pain (LBP), a serious causative underlying pathology-cancer, fracture, or infection-is seldom identified. Some recommended “red flag” screening questions have high false-positive rates, casting doubt on the value of looking for bigger trouble when none is obvious.

Henschke and colleagues evaluated the prevalence of serious pathology and the value of asking red flag screening questions in 1172 patients with LBP being seen by their primary care physician. Participating doctors recorded the responses to 25 questions and then provided an initial diagnosis.

Only 11 patients (0.9%) had serious pathology; 8 of the cases involved fracture. Only 3 of the screening questions provided useful information: prolonged use of corticosteroids, age older than 70 years, and significant trauma. Positive answers to these questions, along with female sex, were moderately associated with incidence of fracture. Most of the screening questions had a high rate of false-positive results, causing the investigators to avoid recommending their use as a worthwhile screening tool in persons with LBP.

The authors noted that the diagnostic accuracy of red flags for all serious pathology is an important but challenging topic for future research.