Some Flags for Low Back Pain Screening Should be Yellow, Not Red
An estimated 85% of all adults will experience low back pain at some point in their lives. So-called “red flag” questions were developed to help primary care providers determine whether a patient’s back pain warranted an escalation of care, either through advanced imaging or referral to a spine specialist. However, in the March 7, 2018 issue of JBJS, Premkumar et al. found that, despite the widespread use of red flag questions, it appears that they have limited clinical usefulness when applied in isolation in a referral spine practice setting.
The authors analyzed the responses to commonly asked red flag questions from more than 9,000 patients presenting to a spine center with low back pain. They found that >90% of the patients had a positive response to at least one of the questions, but only 8% actually had a red flag diagnosis. Furthermore, the authors found that a negative response to one or two of the questions did not preclude a red flag diagnosis. No single red flag question had a sensitivity >75% or a clinically useful negative likelihood ratio—a measure of a screening tool’s ability to rule out a diagnosis.
Importantly, however, certain combinations of positive answers were predictive of specific disease processes. For example, a history of trauma in patients over the age of 50 years was predictive for a diagnosis of spinal compression fracture, and back pain in a patient with a history of a primary oncologic diagnosis should alert physicians to the possibility of metastatic disease. Conversely, the authors say that low back pain that awakens a patient from sleep was not found to be a useful parameter for making any diagnosis.
This is the first large-scale study to evaluate the clinical utility of these questions in the setting of low back pain, and the authors question their usefulness as screening tools. While the concept behind red flag questions remains valid, the rigid application of such questions in decision making regarding advanced imaging or additional testing is not appropriate. The utility of red flag screening questions for low back pain needs additional testing, especially in the primary care setting.
Marc Swiontkowski, MD