Chronic idiopathic urticaria. The diagnostic problem

The causes of chronic urticaria are not revealed in 80—95% of cases. The most important part of the investigation is an anamnesis morbi. Specific laboratory tests should be selected on the basis of diagnostic hypothesis. Tests may include: full blood count, erythrocyte sedimentation rate, C-reactive protein, routine biochemistry, glucose, thyroid function, thyroid autoantibodies, antinuclear antibodies, immunoglobulins, protein electrophoresis, complement C3 and C4 components, cryoglobulins, allergen-specific IgE, serology for infections, stool samples for parasites and urine analysis. Al least 30% of patients with chronic idiopathic urticaria appear to have an autoimmune aetiology. Although a positive serum skin test has a reasonable specificity to establish the autoimmune nature of urticaria, a negative result has high negative predictive value.