"Red flags" under fire

Most clinical practice guidelines for back pain recommend the use of red flags to help identify those patients with a higher likelihood of spinal fracture or malignancy who then become candidates for more extensive diagnostic investigations. There is confusion, however, as the guidelines have produced different lists of red flags to screen for spinal fracture and malignancy. Eight of the guidelines investigated by Koes and colleagues in their review of back pain guidelines, endorsed 26 red flags for fracture and 27 for malignancy. 

None of the eight guidelines endorsed the same set of red flags, for either condition, so it is unclear what clinicians should use in clinical care. Additionally, guidelines generally provide no information on diagnostic accuracy of the endorsed red flags, which limits their value in clinical decision making. Adding to the uncertainty, the same agency can provide inconsistent information on red flags. For example, the National Institute for Health and Care Excellence clinical guideline on the early management of persistent non-specific low back pain does not endorse red flags, whereas the group’s clinical knowledge summary for the management of low back pain does

To resolve the uncertainty around application of red flags in clinical practice, the authors conducted two Cochrane diagnostic test accuracy reviews assessing the accuracy of red flags to screen for the most common forms of serious pathology—spinal fracture and malignancy—in patients with low back pain. They have provided a distilled summary of both reviews to help guide clinical decision making.

Objective To review the evidence on diagnostic accuracy of red flag signs and symptoms to screen for fracture or malignancy in patients presenting with low back pain to primary, secondary, or tertiary care.

Design Systematic review.

Data sources Medline, OldMedline, Embase, and CINAHL from earliest available up to 1 October 2013.

Inclusion criteria Primary diagnostic studies comparing red flags for fracture or malignancy to an acceptable reference standard, published in any language.

Review methods Assessment of study quality and extraction of data was conducted by three independent assessors. Diagnostic accuracy statistics and post-test probabilities were generated for each red flag.

Results We included 14 studies (eight from primary care, two from secondary care, four from tertiary care) evaluating 53 red flags; only five studies evaluated combinations of red flags. Pooling of data was not possible because of index test heterogeneity. Many red flags in current guidelines provide virtually no change in probability of fracture or malignancy or have untested diagnostic accuracy. The red flags with the highest post-test probability for detection of fracture were older age (9%, 95% confidence interval 3% to 25%), prolonged use of corticosteroid drugs (33%, 10% to 67%), severe trauma (11%, 8% to 16%), and presence of a contusion or abrasion (62%, 49% to 74%). Probability of spinal fracture was higher when multiple red flags were present (90%, 34% to 99%). The red flag with the highest post-test probability for detection of spinal malignancy was history of malignancy (33%, 22% to 46%).

Conclusions While several red flags are endorsed in guidelines to screen for fracture or malignancy, only a small subset of these have evidence that they are indeed informative. These findings suggest a need for revision of many current guidelines.

Read the article:

BMJ 2013;347:f7095 BMJ 2013; 347 doi: http://dx.doi.org/10.1136/bmj.f7095 (Published 11 December 2013).