A Raynaud’s nailfold test, also called nailfold capillaroscopy, uses a microscope to examine tiny blood vessels at the base of the fingernails. It shows whether the vessels have a typical pattern or changes such as widening, irregular shapes, or missing capillaries. A normal pattern may support primary Raynaud’s; certain changes may suggest a connective tissue disease, such as systemic sclerosis. Doctors interpret the result alongside symptoms and other tests.
Why is a nailfold test used for Raynaud’s?
Raynaud’s phenomenon occurs when small blood vessels temporarily narrow, usually in response to cold or emotional stress. This can reduce blood flow to the fingers or toes, causing changes in skin colour, coldness, numbness, or tingling. The condition may occur on its own, known as primary Raynaud’s, or be associated with another medical condition, known as secondary Raynaud’s.
The main purpose of nailfold capillaroscopy is to help healthcare professionals distinguish between these patterns by examining the structure of the smallest blood vessels. According to the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), changes in the nailfold capillaries may provide clues to secondary Raynaud’s, including Raynaud’s associated with conditions such as lupus or systemic sclerosis (scleroderma).
What does a normal Raynaud’s nailfold test show?
A normal result generally means that the tiny blood vessels around the nailfold have a usual appearance, with a relatively regular arrangement and no clear pattern of structural damage. The capillaries are present in an expected distribution and do not show the characteristic abnormalities that can occur in certain connective tissue diseases.
A normal pattern may support primary Raynaud’s when it fits the person’s symptoms and examination findings. It is reassuring because it does not show the specific microvascular changes that clinicians look for in some associated diseases. However, a normal nailfold examination cannot rule out every underlying condition or establish the cause of symptoms by itself.
The Cleveland Clinic explains that healthcare professionals use nailfold capillaroscopy to help determine which type of Raynaud’s may be present when the cause is not clear from symptoms and medical history alone.
What abnormalities can the test detect?
An abnormal result means that one or more features of the small blood vessels differ from the expected pattern. The significance depends on which changes are present, how widely they occur across the examined fingers, and whether other clinical findings support the same possibility.
Features that a specialist may look for include:
- Enlarged capillaries: Some blood vessels may appear much wider than expected. Very enlarged vessels are sometimes described as giant capillaries.
- Small areas of bleeding: Tiny spots around a capillary may indicate that blood has leaked from a small vessel.
- Reduced capillary density: Fewer capillaries may be visible in an area than expected, sometimes leaving gaps in the normal arrangement.
- Irregular vessel patterns: The capillaries may become disorganized or show unusual shapes, including branching or bushy-looking vessels.
These findings are particularly relevant when a clinician is assessing for systemic sclerosis, a connective tissue disease that can affect small blood vessels. A peer-reviewed review available through the U.S. National Library of Medicine’s PubMed Central describes enlarged capillaries, small areas of bleeding, capillary loss, and abnormal new vessel patterns among the changes associated with systemic sclerosis.
Not every abnormal feature has the same meaning. A specialist considers the overall pattern rather than relying on one unusual-looking vessel. Nailfold abnormalities can raise suspicion of an associated condition, but they do not automatically mean that a person has systemic sclerosis or another autoimmune disease.
Can an abnormal nailfold test identify the underlying disease?
The test provides information about the structure of small blood vessels, not a complete diagnosis of the disease causing Raynaud’s. Certain patterns can support concern about systemic sclerosis and other connective tissue diseases, but capillaroscopy usually needs to be interpreted alongside the person’s symptoms, medical history, examination, and any other relevant investigations.
If the result is abnormal, a healthcare professional may review whether there are other signs of an underlying condition and decide whether further testing is appropriate. Blood tests may be used to look for evidence of autoimmune disease. These can include an antinuclear antibody (ANA) test, depending on the clinical assessment. Further specialist evaluation may also be recommended when the symptoms or test findings raise concern.
The NIAMS guidance on Raynaud’s diagnosis emphasizes that there is no single test that confirms Raynaud’s phenomenon. Nailfold capillaroscopy and blood tests help clinicians assess its possible cause rather than replacing the broader diagnostic process.
How is the nailfold capillaroscopy test performed?
The examination is usually straightforward and does not involve needles or taking a tissue sample. A clinician or trained specialist examines the skin at the base of the fingernails using a microscope or a video-based imaging device. A small drop of oil may be applied to the nailfold to make the tiny blood vessels easier to see.
The examiner looks at features such as the number, size, shape, and arrangement of the capillaries. Both hands may be examined so that the specialist can assess the overall pattern. The test is generally painless and takes around 20 minutes in the setting described by the Royal Free London NHS Foundation Trust, although the time may vary between clinics.
How should you prepare for the test?
Follow the instructions provided by the clinic. Nail polish, gel polish, and artificial or acrylic nails may obscure the capillaries, so the Royal Free London NHS Foundation Trust advises removing them beforehand if possible. Tell the healthcare professional about any nail changes or recent injury that could affect the examination.
What happens after you receive the results?
The clinician will explain whether the capillaries appear normal or show abnormalities and how the result fits with the reason for testing. A normal result may support primary Raynaud’s in the appropriate clinical context. An abnormal pattern may prompt further assessment for an underlying connective tissue disease, but the next step depends on the findings as a whole.
You may not need additional investigations if the overall assessment is reassuring. If there are concerning features, your clinician may arrange blood tests or refer you to a rheumatologist, a specialist in conditions affecting the joints, muscles, and immune system. The result may also be considered alongside changes in symptoms over time.
Contact a healthcare professional promptly if your fingers remain white or blue despite warming, or if you develop a sore that does not heal or skin breakdown. These changes require assessment regardless of whether a previous nailfold test was normal. The MedlinePlus Medical Encyclopedia identifies persistent colour changes, non-healing sores, and skin breakdown among the reasons to seek medical care for Raynaud’s symptoms.
What is the main takeaway from a Raynaud’s nailfold test?
The test shows the structure and arrangement of the tiny blood vessels at the base of the fingernails. A normal pattern can support primary Raynaud’s, while enlarged vessels, small areas of bleeding, missing capillaries, or disorganized patterns may suggest an associated connective tissue disease. Neither result should be interpreted alone. The most useful conclusion comes from combining the capillaroscopy findings with symptoms, medical history, physical examination, and other tests when needed.