• Diagnose Raynaud's phenomenon if there is a history of clearly demarcated pallor of the digit(s), followed by at least one other colour change (cyanosis and/or erythema). Symptoms are usually precipitated by cold (or, less often, by emotion).
• Raynaud's phenomenon may be confused with:
• Chilblains (perniosis) — red, round, itchy swellings on fingers and toes during cold weather.
• Acrocyanosis — continuous blueness of the hands or feet aggravated by cold.
• Permanently white hands.
• Erythromelalgia — painful redness of the hands or feet caused by paroxysmal dilatation of blood vessels.
• Vascular embolism.
• Livedo reticularis — mottled, cyanotic discolouration of the skin that can be widespread or localized, and physiological or pathological in nature.
• Reflex sympathetic dystrophy (shoulder–hand syndrome) — diffuse persistent pain in an extremity, often associated with vasomotor changes and following an injury.

• Criteria for the diagnosis of Raynaud's phenomenon were conceived by Maurice Raynaud in 1862, and then developed by Allen and Brown [Allen and Brown, 1932]. They are now widely used, and advocated here on the basis of expert opinion from review articles and evidence summaries [Isenberg and Black, 1995; Pope, 2007a; Garcia-Carrasco et al, 2008; Herrick, 2008a; Raynaud's & Scleroderma Association, 2008].
• Differential diagnoses are based on expert opinion from review articles [Isenberg and Black, 1995; Klippel, 2003; Raynaud's & Scleroderma Association, 2008], a textbook [Burns et al, 2004], and an external reviewer.

• Diagnose primary Raynaud's phenomenon if all of the following criteria are met:
• No underlying disease suggested by the history and general physical examination.
• Symmetrical episodes (affects both hands, but not necessarily all fingers).
• No tissue necrosis, ulceration, gangrene, or severe ischaemia.
• Normal nail-fold capillaries (although this may be difficult to determine — see Differentiating between primary and secondary).
• Erythrocyte sedimentation rate (ESR) is normal.
• Anti-nuclear antibody tests are negative.
• If primary Raynaud's phenomenon is diagnosed, initial management can be in primary care.

• Criteria for a diagnosis of primary Raynaud's phenomenon are derived from a classification initially proposed by [LeRoy and Medsger, 1992], and adapted by [Wigley, 2002]. They are widely used and referenced [Gayraud, 2007; Bakst et al, 2008; Herrick, 2008b; Vinjar and Stewart, 2008].

• Suspect secondary Raynaud's phenomenon if any of the following are present:
• Onset at more than 30 years of age.
• Episodes that are intense, painful, or asymmetrical.
• Clinical features suggestive of an underlying disease.
• Positive anti-nuclear antibody tests.
• Abnormal nail-fold capillaries (although this may be difficult to determine — see Differentiating between primary and secondary).
• Digital ulcers, infection, gangrene, or severe ischaemia of one or more digits.
• If secondary Raynaud's phenomenon is suspected, refer to secondary care (usually a rheumatologist).

• Features that suggest a diagnosis of secondary Raynaud's phenomenon are derived from a classification initially proposed by [LeRoy and Medsger, 1992], and adapted by [Wigley, 2002]. They are widely used and referenced [Gayraud, 2007; Bakst et al, 2008; Garcia-Carrasco et al, 2008].

• In the history and systemic enquiry:
• Assess the frequency and severity of attacks.
• Determine whether symptoms are asymmetrical (suggesting secondary) or symmetrical (suggesting primary or secondary).
• Take an occupational history, drug history, and smoking history.
• Ask about any family history of connective tissue disease.
• Ask about symptoms of underlying disease (particularly connective tissue diseases), such as morning joint stiffness, swollen joints, rash, photosensitivity, hair loss, frequent oral or nasal ulcers, significant dry eyes or dry mouth, puffy hands, symptoms of significant oesophageal dysmotility or gastro-oesophageal reflux disease, severe muscle weakness, breathlessness, and weight loss.
• In the examination:
• Look for complications including digital ulcers, infection, or gangrene (which only occur in secondary Raynaud's phenomenon, and usually require immediate admission to hospital for treatment).
• Look for synovitis, puffiness of fingers, tightness of the skin, and livedo reticularis (mottled, cyanotic discolouration that can be associated with connective tissue disease and peripheral vascular diseases).
• Check blood pressure and peripheral pulses in both arms.
• Inspect the nail folds for dilated capillaries. These look like red pen marks, and are most often seen at the cuticles. They are highly suggestive of underlying connective tissue disease.
• This can be done using an otoscope, ophthalmoscope, or dermatoscope (using a drop of oil), if available, but may require experience. See photos on the Archives of Dermatology website.
• If in doubt, refer to a rheumatologist for further evaluation.
• For investigations:
• Do a full blood count (FBC), erythrocyte sedimentation rate (ESR), and check for anti-nuclear antibodies.
• Consider also checking or requesting, if clinically indicated, renal function, liver function tests, serum immunoglobulins and electrophoresis, urinalysis, and hand and chest radiography (although these investigations will be done in secondary care if referral is planned).

• Connective tissue diseases:
• Systemic sclerosis/scleroderma.
• This includes CREST (Calcinosis, Raynaud's phenomenon, Esophageal dysfunction, Sclerodactyly, and Telangiectasia) syndrome, which is now more usually termed 'limited cutaneous systemic sclerosis'.
• Systemic lupus erythematosus.
• Rheumatoid arthritis.
• Sjogren's syndrome.
• Vasculitis (giant cell arteritis, Takayasu's arteritis, malnutrition).
• Mixed or undifferentiated connective-tissue disease.
• Dermatomyositis and polymyositis.
• Vascular occlusive diseases:
• Buerger's disease (thromboangiitis obliterans).
• Arteriosclerosis.
• Thromboembolic disease.
• Drugs:
• Amphetamines and cocaine.
• Beta-blockers.
• Angiotensin-converting enzyme (ACE) inhibitors.
• Cancer chemotherapy (bleomycin, cisplatin, and vinblastine).
• Ciclosporin.
• Ergots/ergot derivatives (ergotamine, methysergide, bromocriptine, cabergoline, pergolide).
• Interferon alpha and beta.
• Combined oral contraceptives.
• Sumatriptan.
• Clonidine.
• Haematological:
• Polycythaemia.
• Monoclonal gammopathies.
• Paraproteinaemia.
• Leukaemia.
• Cryoglobulinaemia.
• Cold agglutinin disease.
• Protein C, protein S, or antithrombin III deficiency.
• Factor V Leiden.
• Occupational/environmental:
• Vibration injury leading to vibration white finger (now referred to as 'hand–arm vibration syndrome').
• Exposure to vinyl polychloride.
• Frostbite/cold injury.
• Ulnar aneurysm (hypothenar hammer syndrome).
• Anatomical:
• Thoracic outlet syndrome (caused by compression from a cervical rib or scalenus anterior muscle).
• Carpal tunnel syndrome.
• Infectious:
• Hepatitis B and C (associated with cryoglobulinaemia).
• Mycoplasma infections (cold agglutinins).
• Parvovirus B19.
• Endocrine:
• Hypothyroidism.
• Phaechromocytoma.
• Carcinoid syndrome.

[Klippel, 2003; Gayraud, 2007; Pope, 2007b; Bakst et al, 2008]

These recommendations are based on:

• Expert opinion from a number of published review articles in relation to methods of detecting an underlying disease [Isenberg and Black, 1995; Wigley, 2002; Gayraud, 2007; Pope, 2007b; Bakst et al, 2008; Raynaud's & Scleroderma Association, 2008] and external reviewer opinion.
• All but one review [Pope, 2007b] advised that anti-nuclear antibodies should be checked routinely in people with Raynaud's phenomenon, regardless of age or gender.
• Evidence from a meta-analysis of studies for predictors of transition from primary to secondary Raynaud's phenomenon, which showed that normal nail-fold capillary pattern and negative anti-nuclear antibodies provide reassurance that a person with primary Raynaud's syndrome is very unlikely to develop an underlying connective tissue disease [Spencer-Green, 1998]. A subsequently-published cohort study also found that positive anti-nuclear antibodies and abnormal nail-fold capillaries were associated with a increased risk of transition to secondary Raynaud's phenomenon [Hirschl et al, 2006].