Physician use of red flags to screen for cancer in patients with new back pain

This review describes the understanding of a common practice for checking for spinal injuries when patients come to a family practice doctor, back pain clinic or emergency room with new back pain.  Doctors usually ask a few questions and examine the back to check for the possibility of a spinal tumor.  The reason for this check for tumors is that the treatment is different for common back pain and tumors.  Tumors are usually diagnosed with an x-ray, magnetic resonance imaging (MRI) or computed tomography (CT), then treated with surgery and/or chemotherapy. Common back pain is treated with exercise, spinal manipulation, and pain relievers; x-rays, CT and MRI scans are not useful for diagnosis.  Tumors are rare, being the cause of back pain in approximately 1% of new back pain visits to family doctors.  Only about 10% of these cancers are new cases; 90% are recurrences of cancers from other parts of the body (metastases).

Six family practice studies including over 6,600 back pain patients found 21 tumors (0.3%).  One study on back pain diagnosed in an emergency room and one on back pain in a spine clinic included 482 and 257 patients.  The family practice studies described 15 different questions and physical exam tests that have been used to screen for spinal tumors.  Most of the 15 were not accurate.  A previous history of cancer is a very useful indicator.  Other facts that may indicate cancer are age greater than 50, no prior history of back pain, and failure to improve after one month.  These are most likely useful when combined, or with other indicators such as a history of cancer.  By themselves, these three questions would result in over-testing of patients without cancer.

The worst effects of low quality red flag screening are overtreatment and undertreatment.  If the tests are not accurate, patients without a tumor may get an x-ray, MRI, bone scan or CT scan that they don’t need—unnecessary exposure to x-rays, extra worry for the patient and extra cost.  At the other extreme (and much less common), it might be possible to miss a real tumor, and cause the patient to have extra time without the best treatment.

Most of the studies were of low or moderate quality and did not use an MRI, the most accurate imaging test, to confirm the presence or absence of a tumor, so more research is needed to identify the best combination of questions and examination methods.

Authors' conclusions: 

For most "red flags," there is insufficient evidence to provide recommendations regarding their diagnostic accuracy or usefulness for detecting spinal malignancy. The available evidence indicates that in patients with LBP, an indication of spinal malignancy should not be based on the results of one single "red flag" question. Further research to evaluate the performance of different combinations of tests is recommended.

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Background: 

The identification of serious pathologies, such as spinal malignancy, is one of the primary purposes of the clinical assessment of patients with low-back pain (LBP). Clinical guidelines recommend awareness of "red flag" features from the patient's clinical history and physical examination to achieve this. However, there are limited empirical data on the diagnostic accuracy of these features and there remains very little information on how best to use them in clinical practice.

Objectives: 

To assess the diagnostic performance of clinical characteristics identified by taking a clinical history and conducting a physical examination ("red flags") to screen for spinal malignancy in patients presenting with LBP.

Search strategy: 

We searched electronic databases for primary studies (MEDLINE, EMBASE, and CINAHL) and systematic reviews (PubMed and Medion) from the earliest date until 1 April 2012. Forward and backward citation searching of eligible articles was also performed.

Selection criteria: 

We considered studies if they compared the results of history taking and physical examination on patients with LBP with those of diagnostic imaging (magnetic resonance imaging, computed tomography, myelography).

Data collection and analysis: 

Two review authors independently assessed the quality of each included study with the QUality Assessment of Diagnostic Accuracy Studies (QUADAS) tool and extracted details on patient characteristics, study design, index tests, and reference standard. Diagnostic accuracy data were presented as sensitivities and specificities with 95% confidence intervals for all index tests.

Main results: 

We included eight cohort studies of which six were performed in primary care (total number of patients; n = 6622), one study was from an accident and emergency setting (n = 482), and one study was from a secondary care setting (n = 257). In the six primary care studies, the prevalence of spinal malignancy ranged from 0% to 0.66%. Overall, data from 20 index tests were extracted and presented, however only seven of these were evaluated by more than one study. Because of the limited number of studies and clinical heterogeneity, statistical pooling of diagnostic accuracy data was not performed.

There was some evidence from individual studies that having a previous history of cancer meaningfully increases the probability of malignancy. Most "red flags" such as insidious onset, age > 50, and failure to improve after one month have high false positive rates.

All of the tests were evaluated in isolation and no study presented data on a combination of positive tests to identify spinal malignancy.

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