Red herring or red flag, that is the question in low back pain

Primary care clinicians see lots of low back pain. It is one of the most common symptoms that brings patients to our offices. It is safe to say the spine is one of the more poorly designed organs in the human body. Arcing this way and back again, it is an evolutionary remnant bequeathed to us from our quadruped ancestors. Its structure virtually guarantees malfunction at some point in life, as we humans try to move in bipedal fashion through our complex environment.

Most of the time, fortunately, low back pain is a temporary condition due to transient mechanical perturbations in the para-spinous muscles, ligaments, disks, or other structures of the spine and back. Our general approach to diagnosis and treatment is appropriately conservative, since embarking on an extensive work-up including imaging frequently yields red herrings, which can cause unnecessary angst in our patients and uncertainty in ourselves.

Nonetheless, we have all been trained to watch for red flags when assessing patients with low back pain. Red flags, as opposed to red herrings, are indicators of potentially serious etiologies when a patient presents with low back pain. When a red flag is present, we need to be more detailed in our assessments, to rule out diagnoses like malignancy, infection, or fracture as the source of the back pain.

What markers qualify as true red flags? A recent review in the British Medical Journal examined 14 studies which looked at this question for cancer and fracture, but not for infection. In the case of malignancy, they assessed 24 possible red flags, but only one reached the level of significance for utility: past history of cancer. Age, unexplained weight loss, failure to improve after one month of treatment – none of these turned out to be significant markers of possible underlying malignancy. In the case of fracture, 29 possible red flags were looked at. The only useful ones were presence of an abrasion or contusion, chronic use of steroids, trauma, and age greater than 64.

The care of any patient must of course be individualized. Guidelines need to be applied with wisdom to a person’s specific situation. But the database we clinicians use can be strengthened by reviews such as this one in the BMJ as we do our best to apply science to the art of medicine.

Richard Fleming, MD

Downie A.,, BMJ Dec 11, 2013

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