Despite the similarity of initial symptoms in primary Raynaud's phenomenon (PRP) and secondary Raynaud's phenomenon (SRP), the long-term implications of SRP mean that it is critical for there to be more effective assessments that can accurately specify which of the two a person may have.
Raynaud's is characterised by the recurrent constriction of digital arteries in the fingers and toes, as well as at times the nose, ears and lips; this leads to colour changes from white, blue and red. This can be caused by sudden temperature changes or as a stress response. Between 5 – 10% of the world's population are thought to live with either PRP or SRP. Whilst both can be extremely debilitating for the individual, PRP is generally thought of as being a benign condition that is idiopathic (no underlying cause), whereas SRP is associated with a range of several connective tissue diseases (CTD), especially systemic sclerosis (SSc). 90% of SSc patients first present with Raynaud's, and this may precede diagnosis of SSc for many years.
Currently, the suggested criteria for diagnosing PRP includes no sign of necrosis, ulceration or gangrene, and negative tests for antinuclear antibodies (ANA). If a person has SRP, it is likely that the ANA blood test comes back positive. A positive ANA blood test result suggests that the patient has, or is at risk of developing, an auto-immune condition. This category includes: diabetes (type 1), hypothyroidism, hyperthyroidism, lupus, and SSc. If there is a positive result, a rheumatologist may decide to carry out morphological tests, such as nailfold videocapillaroscopy (NVC), and functional tests (laser tools and thermography) for further investigation. This is dependent on the hospital's resources, as these tools are still considered to be 'new innovations' and their utilisation is not widespread across the UK as of yet.
A study published in Frontiers in Pharmacology, entitled 'Innovations in the Assessment of Primary and Secondary Raynaud's Phenomenon', aimed to review the above techniques to evaluate their ability to make a correct diagnosis, as well as assess treatment for Raynaud's over a period of time, and investigate blood perfusion. 'Blood perfusion' refers to the delivery of oxygenated blood from the arteries to the capillary bed in tissues, which allows cells to survive and grow.
The review demonstrated that NVC is able to distinguish between PRP, SRP and healthy subjects; this is achieved by detecting morphological abnormalities in the nailfold capillary bed. Nailfold capillaries in PRP are usually normal in shape and have no dramatic alteration in their size i.e. giant capillaries. Abnormal nailfold capillaroscopic images were included in the 2013 European League Against Rheumatism and American College of Rheumatology classification criteria for SSc for diagnostic purposes. It is also suggested that follow-up NVC analysis should be performed every 6 months in PRP patients, to monitor any potential progression to SRP. NVC cannot be used to measure blood perfusion, but this can be achieved by other methods, such as laser techniques and thermography.
Laser Doppler Flowmetry (LDF) evaluates blood flow at a single location, providing an indication of blood perfusion. Laser Doppler Imaging (LDI) may be more effective, as it can assess more than one area and can be used to evaluate the microcirculatory blood flow. It can also aid in the differentiation of PRP and SRP within the context of scleroderma.
Thermal imaging is an indirect method of detecting Raynaud's, making use of a thermal camera to display the skin temperature. It has been successful in evaluating RP in several studies however, and it has demonstrated capabilities in distinguishing between PRP and SRP, but is less able to detect blood perfusion.
It has been proposed by various clinical research groups that a combination technique incorporating NVC, LDI and thermal imaging would be the most effective diagnostic tool, however this is not a widely available resource. The non-invasive assessment of morphological and functional features affecting circulation may supplement the physical examination and help to provide a quick, accurate diagnosis – thus paving the way for faster and effective treatment for both PRP and SRP.
Studies such as these reiterate the necessity for clinicians to take Raynaud's seriously in all its presentations, especially because on occasion it is likely to be, what the researchers stated in this study, a 'precocious cloaked clinical sign' of abnormal microcirculation and a risk factor for the development of a CTD, especially SSc. It is important to remember that whilst there is no curative treatment for all individuals living with Raynaud's due to its heterogeneity, there are management approaches that can be taken to improve and maintain quality of life. Early detection and immediate intervention are at the crux of enabling this, two of the four key themes that SRUK will be focussing on in the next 5 years, as per our Research Strategy.
If you are interested in helping SRUK to fund more work like this, then please visit our donations page here: https://www.sruk.co.uk/donate/. We rely on the generosity of our community to continue to support groundbreaking research in both scleroderma and Raynaud's.
If you would like information on how Raynaud's is diagnosed, then please visit: https://www.sruk.co.uk/raynauds/raynauds-getting-diagnosed/.
Information on another new piece of research on Raynaud's can be found here: https://www.sruk.co.uk/about-us/news/do-we-need-new-way-assess-raynauds-phenomenon-clin/
