Incremental build-up food challenge - a new diagnostic approach to evaluate pseudoallergic reactions in chronic urticaria: a pilot study

The remission rate of patients with chronic urticaria (CU) due to elimination diets varies between 31% and 71%. However, the diagnostic value of subsequent traditional oral provocation tests with food additives in capsules remains unsatisfactory. A newly incremental build-up food challenge (IBUF) for patients with CU was designed and implemented in an open pilot study. Primary endpoint was the percentage of patients developing urticaria during at least one step of IBUF after an initial complete remission due to a pseudoallergen-free elimination diet. In total, 153 patients with CU were submitted for 5 weeks to a pseudoallergen-free diet. All patients with remission were included to the 6-week IBUF protocol, containing pseudoallergen-rich foods in a systematic and additive manner. The recurrence and severity of CU was evaluated by urticaria score. Subjective disturbance and quality of life were evaluated by patients' diary, visual analogue scale and quality of life questionnaire (CU-Q(2)oL). Subsequently, patients were followed up for 3-24 months after IBUF by a telephone interview. A total of 104 patients completed the pseudoallergen-free diet, whereby 51% reported partial, 17% complete and 32% no remission due to the diet. All diet responders showed a decrease in subjective impairment, urticaria and quality of life score (P < 0.001 each). Eighty-six percent (12/14) of the patients reaching complete remission, showed a recurrence of urticaria symptoms during the IBUF protocol. Fifty-eight percent (7/12) of these patients still remained free of symptoms due to avoidance of IBUF-identified foods at telephone follow-up. In patients with partial remission to pseudoallergen-free diet, however, IBUF did not provide information about the cause of urticaria symptoms. The newly developed IBUF protocol seemed to be a promising method for identifying individually incompatible foods in some CU patients. IBUF should be verified by randomized controlled trials to gain additional evidence for its diagnostic value.