Patients with asthma may develop bronchoconstriction after ingestion of sulfites. We studied the sensitivity and specificity of an oral provocation challenge with metabisulfite to detect a sulfite-sensitive asthma.
We performed an oral dose-response metabisulfite challenge in 44 patients with a history of sulfite-sensitive asthma, 27 patients with asthma but without a history of sulfite sensitivity, and 8 control subjects without asthma. Metabisulfite was administered in capsules in a single-blind manner. Airway response was assessed by FEV decline, measured 30' after each dose.
Thirty-nine percent of patients with a history of sulfite-sensitive asthma demonstrated a significant bronchoconstriction after ingestion of metabisulfite, whereas patients without an appropriate history and control subjects did not respond to the challenge.
The oral metabisulfite challenge exhibits a high specificity (100%) but low sensitivity of about 40%. Nonetheless, taking into account the uncertainties in the patients' history of sulfite-sensitive asthma, the oral metabisulfite challenge as performed by us is a useful method for the diagnosis of sulfite sensitive asthma.