At least three out of five criteria yields sensitivity and specificity of 95 and 91%: 

Age at onset ≥ 50 years
New onset headache with localized tenderness
Temporal artery tenderness or decreased pulsation
Elevated ESR ≥ 50 mm/hour Westergren
Temporal artery biopsy showing vasculitis with mononuclear cell infiltrate or granulomatous inflammation, usually with multinucleated giant cells

Medium vessel vasculitis
These conditions are sometimes considered together with the small vessel vasculitides.Polyarteritis nodosa (PAN). Systemic necrotizing vasculitis and aneurysm formation affecting both medium and small arteries. If only small vessels are affected, it is called microscopic polyangiitis, although it is more associated with granulomatosis with polyangiitis than to classic PAN. At least 3 out of 10 criteria yields sensitivity and specificity of 82 and 87%:

Unexplained weight loss > 4 kg
Livedo reticularis
Testicular pain
Myalgias, weakness
Abdominal pain, diarrhea, and GI bleeding
Mononeuropathy or polyneuropathy
New onset diastolic blood pressure > 90 mmHg
Elevated serum blood urea nitrogen (> 40 mg/dL) or serum creatinine (> 1.5 mg/dL)
Hepatitis B infection
Arteriographic abnormalities
Arterial biopsy showing polymorphonuclear cellsKawasaki disease. Usually in children (age<4), it affects large, medium, and small vessels, prominently the coronary arteries. Associated with a mucocutaneous lymph node syndrome. Diagnosis requires fever lasting five days or more with at least four out of five criteria:

Bilateral conjunctival injection
Injected or fissured lips, injected pharynx, or strawberry tongue
Erythema of palms/soles, edema of hands/feet, periungual desquamation
Polymorphous rash
Cervical lymphadenopathy (at least one node > 1.5 cm)Isolated cerebral vasculitis. Affects medium and small arteries over a diffuse CNS area, without symptomatic extracranial vessel involvement. Patients have CNS symptoms as well as cerebral vasculitis by angiography and leptomeningeal biopsy.
Usually due to hepatitis B and C, human immunodeficiency virus, cytomegalovirus, Epstein–Barr virus, and parvovirus B19. Signs and symptoms
Patients usually present with systemic symptoms with single or multiorgan dysfunction. Common (and nonspecific) complaints include fatigue, weakness, fever, joint pains, abdominal pain, hypertension, chronic kidney disease, and neurologic dysfunction. The following symptoms should raise a strong suspicion of a vasculitis:

Mononeuritis multiplex. Also known as asymmetric polyneuropathy, in a non-diabetic this is suggestive of vasculitis. Palpable purpura. If patients have this in isolation, it is most likely due to cutaneous leukocytoclastic vasculitis. If the purpura is in combination with systemic organ involvement, it is most likely to be Henoch–Schönlein purpura or microscopic polyangiitis. Pulmonary-renal syndrome. Individuals who are coughing up blood and have kidney involvement are likely to have granulomatosis with polyangiitis, microscopic polyangiitis, or anti-GBM disease (Goodpasture syndrome). Diagnosis
A detailed history is important to elicit any recent medications, any risk of hepatitis infection, or any recent diagnosis with a connective tissue disorder such as systemic lupus erythematosus (SLE). A thorough physical exam is needed as usual. Lab tests. Basic lab tests may include a complete blood count, chemiestries (look for creatinine), creatine phosphokinase level, liver function tests, erythrocyte sedimentation rate, hepatitis serologies, urinalysis, chest X-ray, and an electrocardiogram. Additional, more specific tests include:
Antinuclear antibody test can detect an underlying connective tissue disorder, especially lupus erythematosus
Complement levels that are low can suggest mixed cryoglobulinemia, hepatitis C infection, and lupus erythematosus], but not most other vasculitides.