An Introduction to Red Flags in Serious Pathology
Only around 1% of all musculoskeletal presentations in primary care will be due to serious pathology. Such pathologies include spinal infection, cauda equina, fracture, malignancy and spondyloarthropathies.
Yet despite the low incidence rates, these conditions should be considered as differential diagnoses when individuals present with back pain - particularly if the patient is not responding in an expected way or is starting to worsen. Identifying serious pathology early on is very important for a number of reasons:
- Prognosis improves with early diagnosis
- Patients tolerate treatment better
- Outcomes are better
- Quality of life is better maintained
However, it can be challenging identifying serious pathologies as they often masquerade as musculoskeletal conditions, particularly in the early stages of disease. As a disease progresses, it becomes easier to identify as patients become systemically unwell.
What are Red Flags?
Red flags are specific attributes derived from a patient's medical history and the clinical exam that are usually linked with a high risk of having a serious disorder like an infection, cancer, or a fracture. Red flags are not diagnostic tests and they don't necessarily predict diagnosis or prognosis but are rather clinical prediction guides. Their main function is to raise the therapist's suspicion when they are combined. 
The flag system describes clinical and psychological flags and is comprised of red, orange, yellow, blue and black. Clinical flags are common to many areas of health – for example, red flags are indicators of possible serious pathology such as inflammatory or neurological conditions, structural musculoskeletal damage or disorders, circulatory problems, suspected infections, tumours or systemic disease. If suspected, these require urgent further investigation and often surgical referral.
Red flag screening questions were developed to help detect serious spinal pathology. However, specific red flag questions are not used consistently across guidelines and there is little evidence to support their use. Moreover, there are 163 different items that could be considered to be red flags, all of which are subject to interpretation. Because of these factors, the benefit of using red flags has been questioned. Yet a clinician still needs to determine if a patient’s presenting condition is suitable for conservative management or if a referral is necessary. Thus, despite a lack of consensus, red flags are still considered the most reliable clinical indicator of potential serious pathology.
Common Red Flags
- Age over 50 years
- Progressive symptoms
- Thoracic pain
- Past history of cancer
- Weight loss
- Drug abuse
- Night pain
- Systemically unwell (fever)
- Night sweats
Evidence for Red Flags
- Recent trauma and age >50 is associated with vertebral fracture.
- Similarly, a “history of cancer” and “strong clinical suspicion” have empirical evidence of high diagnostic accuracy for malignancy.
On the whole, red flag screening for low back pain has not been used successfully.
- Red flags generally have poor diagnostic accuracy
- Lack of consensus in guidelines as to which red flags should be used or when clinicians should act.
According to Cook et al there are four key reasons why red flag screening has not been successful:
- Red flag symptoms do not rule out serious spinal pathology, but they do not identify it either. The clinical tests for red flags do not have low negative likelihood ratios, which means they cannot "rule out" a red flag even when the test is negative.
- There is great variability in how red flags are defined, which limits research and clinical progress.
- Most guidelines recommend screening for red flags and then encourage anyone who presents with red flags to undergo extensive diagnostic testing, even if only one symptom is present. However, at least 80% of patients will have at least one red flag. Moreover, it is important to remember that "true screening" really only can occur in a pre-clinical phase when there are no outward symptoms of a disease (ie before a physiotherapist would see a patient). Thus, our red flag "screening" is actually a management strategy that does not involve any screening in the medical sense.
- Clinicians are not screening for red flags, but rather are managing the conditions that they see. And as Cook et al note, red flag findings are more related to prognosis than to serious pathology (ie fracture, cancer).
Alternative Approach for Clinical Practice
It is still recommended that health professionals use red flags to identify potential serious pathology.
- Recent research focused on creating an alternative approach to red flag screening.
- A key aspect of this framework is a greater focus on the context of the red flag.
- A patient's entire history must be considered and clinicians must ask for enough detail to understand the context behind answers to red flag screening questions.
- History of cancer - important to enquire where the original cancer was: breast, prostate and lung would heighten the index of suspicion of metastases in the spine.
- Weight loss - unexplained weight loss is a cause for concern (if a patient has been on a diet or exercising more, weight loss is to be expected or if certain new medications or pain are suppressing a patient’s appetite.
- Night pain - many patients with back pain will complain of night pain. Important to find out more about the quality of this pain. A patient who is able to get back to sleep will not generate the same level of suspicion as a patient who cannot get back to sleep or has to get up to sit in a chair to get back to sleep.
Level of Concern
The level of concern is considered. The framework encourages clinicians to not simply rely on one red flag, but rather to consider the context of the patient and the context of the red flag/s, including symptom progression and co-morbidities.
The clinician needs to decide if there is a level of concern. If there is none, management can begin. If there is some concern, the clinician could consider a trial treatment but will need to monitor the patient over time and revise the management if necessary. Red flags should be regularly considered and re-evaluated. It is not enough to simply consider red flags at the initial assessment.
If there are more concerning features, the clinician needs to consider their urgency. Is it a medical emergency (eg cauda equina) that requires immediate action or potential metastases, which could wait a few days, but still requires urgent referral?
PathwayThe pathway helps clinicians understand what they should do with patients who present with concerning features. This pathway is moveable and flexible - a patient can move between pathways.
- It is important to consider serious pathology as a differential diagnosis. Clinicians need to consider how a red flag presents for a particular patient. Context is essential.
- Red flags should be re-evaluated at every session.
- It is important to identify which pathway a patient should be on, to ensure that they receive the correct care in a timely fashion.
- Finucane L. An Introduction to Red Flags in Serious Pathology. Physioplus 2020.
- Finucane L, Downie A, Mercer C, Greenhalgh S.M., Boissonnault W.G., Pool-Goudzwaard A.L., Leech R.L. and Selfe J. International Framework for Red Flags for Potential Serious Spinal Pathologies. [Position Statement] 22 May 2020. Journal of Orthopaedic & Sports Physical Therapy
- Premkumar A, Godfrey W, Gottschalk MB, Boden SD. Red Flags for Low Back Pain Are Not Always Really Red. J Bone Jt Surg. 2018;100(5):368–74.
- Cook CE, George S Z, Reiman M P. Red flag screening for low back pain: nothing to see here, move along: a narrative review. British Journal of Sports Medicine. 2018;52: 493–496.
- Yusuf M, Finucane L, Selfe J. Red flags for the early detection of spinal infection in low back pain. BMC Musculoskeletal Disorders. 2019; 20(606). Available at: https://bmcmusculoskeletdisord.biomedcentral.com/articles/10.1186/s12891-019-2949-6
- Verhagen AP, Downie A, Maher CG, Koes BW. Most red flags for malignancy in low back pain guidelines lack empirical support: a systematic review. Pain. 2017;158(10):1860-8.
- Verhagen AP, Downie A, Popal N, Maher C, Koes BW. Red flags presented in current low back pain guidelines: a review. European Spine Journal. 2016 Sep 1;25(9):2788-802.
- Finucane L, Selfe J, Mercer C, Greenhalgh S, Downie A, Pool A et al. An evidence informed clinical reasoning framework for clinicians in the face of serious pathology in the spine course slide. Physioplus 2020.