Red flags

Red flags which require immediate action

Cauda equina

Urinary retention, faecal incontinence, saddle anaesthesia, bilateral neurological signs

Infection

Unexplained fever, recent infection (UTI, skin), IV drug abuse, immunosuppression

Abdominal aortic aneurysm

Male, smoker, 65-75 years old

Red flags which should be monitored

Neurologic

Progressive motor weakness, or motor deficits at multiple levels

Cancer

Strong risk factors: history of cancer (especially breast, prostate, lung, thyroid, kidney); strong clinical suspicion

Fracture

Combination of: female; over 70 years old; significant trauma; prolonged corticosteroid use; presence of contusion or abrasion

Ankylosing spondylitis

Persistent symptoms alternating buttock pain, morning stiffness that improves with movement, better with exercise, awaking with pain in the second part of the night, onset under 40 years old

Acute low back pain can be caused by pathology, but this is very rare.

Red flags are a well-established screening mechanism but many commonly used flags do not meaningfully increase the likelihood of pathology being present.

Screening for pathology also has negative side effects. These include significant radiation exposure, anxiety due to expectation of pathology or incidental findings, and unnecessary subsequent interventions.

“I now (long pause) try to see that in perspective of the harm that you cause by trying to exclude serious pathology all the time”

GP WITH 28 YEARS EXPERIENCE

It is important to differentiate between pathology which requires immediate action in order to change patient outcome (e.g. cauda equina syndrome, infection, abdominal aneurysm), and pathology for which delaying identification by a few weeks will not significantly affect the outcome (e.g. compression fractures, spinal metastases, ankylosing spondylitis).

Although it is important that prolonged treatment is not inappropriately directed at pain of pathological origin, the relative risk of missing these conditions is low compared to the risks of excessive screening.