Serum Immunoglobulin G is a Marker for the Risk of Opportunistic Infection in Steroid-dependent Severe Asthmatic Patients

Background Approximately 10% of asthmatic patients are refractory to inhaled corticosteroids and therefore need long-term oral corticosteroid therapy, which is associated with a risk of opportunistic infections due to immunosuppression. Objective To ascertain the applicability of serum Immunoglobulin G (IgG) as a marker for predicting the risk of opportunistic infections in patients undergoing oral corticosteroid therapy. Methods Three thousand asthmatics were screened, and 14 patients who had been administered daily oral corticosteroids for more than two years were enrolled. The patients enrolled were maintained under observation with ordinary check-ups and treatments for one year. After the observation period, the patients were divided into two groups according to the presence (OPI) or absence (Non-OPI) of opportunistic infections during the period. The differences in the clinical parameters between the groups were investigated. Results There were no statistically significant differences in age, forced expiratory volume in 1 second (FEV1), smoking status or serum albumin between the groups. The serum IgG level of the OPI group was significantly lower than that of the Non-OPI group (567.2±151.1 mg/dL vs. 931.6±198.8 mg/dL, p