Serum immunoglobulin G is a marker for the risk of opportunistic infection in steroid-dependent severe asthmatic patients

Abstract

Background Approximately 10% of asthmatic patients are refractory to inhaled corticosteroids and there-fore 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 observa-tion with ordinary check-ups and treatments for one year. After the observation period, the patients were di-vided into two groups according to the presence (OPI) or absence (Non-OPI) of opportunistic infections dur-ing 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<0.01). The average total dose of corticosteroids administered during the one year period was higher in the OPI group (2,633±554.2 mg) than that in the Non-OPI group (1,793±466.2 mg) (p<0.05). There was a significant correlation between the serum IgG and total dose of corticosteroids administered during the one-year period (r=-0.75, p<0.01). The area under the receiver operating characteristic curve regarding the serum IgG and in-cidence of opportunistic infections was 0.97, which suggests that the serum IgG level has a high accuracy for predicting the risk of opportunistic infections. Conclusion The serum IgG was therefore found to be a useful marker for predicting the risk of opportunis-tic infections in steroid-dependent asthmatics. © 2012 The Japanese Society of Internal Medicine.