The effectiveness of a history-based diagnostic approach in chronic urticaria and angioedema

OBJECTIVE: To assess the value of extensive laboratory screening for the identification of causes in patients with chronic urticaria and/or angioedema. DESIGN: In a prospective study involving 220 patients, 2 diagnostic strategies were compared: the combination of detailed history taking and limited laboratory investigations vs detailed history taking and extensive laboratory screening. The results of the extensive screening program were initially kept secret from the patients and the physicians. Later, all results were disclosed, and an investigation was undertaken to find out whether this information changed the initial diagnosis. The patients were followed up for 1 year to evaluate the results of interventions and to detect latent causes. SETTING: The study was performed in the outpatient department of a secondary and tertiary care center with institutional practice. PATIENTS: A total of 238 consecutive new patients with chronic urticaria and/or angioedema edema were referred; 18 of them refused participation. One patient was unavailable for follow-up. MAIN OUTCOME MEASURE: The difference in the number of identified causes between both approaches and the nature of the causes that would have been missed by omitting extensive laboratory screening. RESULTS: With a questionnaire and the limited laboratory tests, a cause was found in 45.9% of the patients, compared with 52.7% with the questionnaire and the extended screening program. Except for one parasitic infection, missed diagnoses were mainly adverse reactions to drugs or food detected by standard elimination procedures, not by laboratory investigations. CONCLUSION: Routine laboratory screening did not contribute substantially to the diagnosis of chronic urticaria or to the detection of underlying disorders