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My GP won’t get an MRI done – why?

My low-back is really painful and I want an MRI done – my GP says no.  Why?

The background:

A recent study called Red Flag Screening for Low Back Pain was carried out by these three:  Cook CE, George SZ & Reiman MP, and published in the British Journal of Sports Medicine 2018 (52: 493–496).  Let me assure you that this is no slouch of a journal and this is good science.

We, clinicians who treat low back pain (LBP), use differential diagnostics to improve the likelihood of providing the appropriate care to our patients.  What we are looking for is the ‘why?’; so the underlying condition.  We then address this problem and get things working properly again.  We are also screening for serious primary pathology such as cancer or fracture.  This is a form of preliminary screening that may then indicate the need for more diagnostic testing before treatment is delivered.

This screening is called Red Flag Screening.  This term was first used by Berry over 90 years ago and involves such things as:  age < 45, night/morning pain, family history, etc.  However, researchers have concluded that screening for the Red Flags associated with low back pain does not work.

And the authors suggest this is why Red Flags are not valuable:

  • Reason 1: red flag symptoms neither rule out nor identify serious pathology. There is some serious statistical process here using sensitivity and specificity values that you need a PhD to understand.  The upshot is the tests are not good enough.
  • Reason 2: variability in definitions for red flag symptoms greatly limits research and clinical progress in this area. Due to the startlingly low prevalence of serious conditions, studies evaluating symptoms and tests for Red Flags are very difficult to conduct.  This would mean prohibitively large sample sizes for a valuable study. 
  • Reason 3: LBP guidelines do not help
    The vast majority of guidelines for treatment of low back pain recommend the use of red flag screening for determining the presence of spinal fracture or malignancy. However, an overview of guidelines for non-specific LBP revealed 8 guidelines endorsing 27 separate Red Flags for malignancy and 26 for fracture.  At the same time, none of the 8 guidelines endorsed the same set of Red Flags.  So, there is no consistent set of rules to use to identify possible underlying conditions.  Additionally, the use of traditional Red Flags for imaging can lead to significant overuse of imaging and potentially inappropriate clinical reasoning.
  • Reason 4: we do not actually screen for Red Flags; they manage LBP conditions they see. Low back pain is itself a symptom of an underlying condition and not a diagnosis.  It is not affiliated with a serious pathology.  It will often have symptoms similar to competing diagnoses such as fracture or cancer.  Many Red Flags associated with LBP are more prevalent in an older population, which also frequently have other orthopaedic-related LBP.  Indeed, a definitive set of signs and symptoms that are unique to serious pathology of the low back has not been identified. 

So, the tests don’t work and so why get an MRI done?

So, the Red Flags don’t work – what should be done?

The authors offer 3 recommendations regarding testing for Red Flags:red flags and low-back pain

  • Watchful waiting: rather than ordering early diagnostic testing, clinicians are encouraged to use watchful waiting.  This allows time to pass before initiating medical intervention.  Early testing may, in fact, be detrimental to patients with LBP.  Early detection may also increase the incidence of several diseases but for many, the mortality rate remains unchanged.  As such, the usefulness of early detection may not be justified.  The authors recommend careful monitoring of symptoms, watching for changes over time.
  • Value-based care: the costs associated with the episode of care for LBP can escalate rapidly when diagnostic imaging like MRI are added.  This can significantly affect the value-based aspects of care.  The authors advocate for the careful consideration of value-based care before ordering expensive and potentially unnecessary tests.
  • Link red flag testing with health status rather than diagnostic testing: up to 94% of patients presenting to a general practice will present with abnormal MRI findings, while only 3% are likely to have an underlying serious pathology. The serious condition most likely to be present in this population is vertebral fracture.  There are reliable clinical tests for this.  So, linking tests to the patient’s health status, rather than potential Red Flags, could lead to a decrease in the use of diagnostic imaging, and an overall improvement in the episode of care.

So, the Red Flag screening tests don’t really tell you anything useful.  Using them as a basis for getting further expensive testing done is unhelpful.  If you do get a test done nearly everyone presents with abnormal MRI findings so this tells you nothing.  Only 3% of those who undergo MRI have something significant.  Of these, detecting this makes no difference in the long run.

And, that’s why your GP will say no.

Still, it is good to know:

up to 94% of patients presenting to a general practice will present with abnormal MRI findings, while only 3% are likely to have an underlying serious pathology

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