**8. Diagnosis**

A through history is the most important tool in the diagnosis of urticaria. Duration, timing and localization of lesions, history of a recent viral infection, recent insect bite, medications, suspected foods, associated systemic symptoms, such as fever and arthralgia, and response to previous treatments should be questioned [5, 13]. In majority of cases of acute urticaria, history taking and physical examination is sufficient for the diagnosis. Further investigations are generally not required in patients with acute urticaria except those with a clinical history or physical examination suggesting an underlying cause, such as upper respiratory tract infection, food- or drug-induced urticaria [8]. Skin prick tests and serumspecific IgE tests can be used to confirm allergic reaction to foods, latex and certain antibiotics [5].

In chronic urticaria, complete blood count, liver enzymes, urinalysis and thyroid function tests can be checked; however, these laboratory tests are of minor significance, if there is not a suspected underlying etiology for persistent urticarial lesions [13, 21].

Skin testing to aeroallergens can be of value only if the patient has concomitant allergic rhinitis and/or asthma. If the patient reports a specific food to be strongly related with the attacks, a serologic test to the specific food can be performed. Serologic testing would be more reliable than skin testing as an interpretation of wheal and flare response would be misleading in patients under recurrent bouts of urticaria [16].

Autologous serum skin test is a practical clinical test to detect circulating functional autoantibodies in patients with chronic urticaria. The test is performed by intradermal injection of patient's own serum obtained while the patient is symptomatic and injection of 0.9% saline on volar aspect of the forearm. It is of importance to stop antihistamines 2 days before application. A positive autologous serum skin test is defined as a red serum-induced wheal having a diameter greater than 1.5 mm than the saline-induced wheal at 30 min. The test is performed when an immunomodulatory treatment is planned for patients with severe chronic urticaria. However, this is a controversial issue as the presence or absence of autoantibodies does not predict efficacy to most therapies [5, 16]. Basophil histamine release assays, western blot analysis or ELISA are also used to detect autoantibodies. However, these tests are sophisticated tests not readily available to most clinicians [22].

Urticaria activity score (UAS) is commonly used to assess disease activity and treatment response in patients with chronic urticaria. UAS is calculated based on the daily number of wheals (1–3 points) and the intensity of pruritus (0–3 points) and ranges from 0 to 6 [23]. UAS7 is calculated by summing UAS recorded by the patient on 7 consecutive days. A UAS7 score of less than 7 indicates control of disease, whereas a score exceeding 28 indicates poorly controlled symptoms [24].
