Serum and bronchoalveolar IgG against A60 and 38kDa antigens in the diagnosis of tuberculosis

SETTING: The ELISA test is generally accepted for serodiagnosis of tuberculosis. Its sensitivity and specificity depend on the antigen used and data are not always concordant. In some patients suspected of tuberculosis, sarcoidosis or lung cancer, bronchoalveolar lavage (BAL) is performed. BAL fluid (BALF) contains immunoglobulins - their source is transudation from the serum but local IgG synthesis of Ige is not excluded. OBJECTIVE: The comparison of BALF versus serum in the serodiagnosis of pulmonary tuberculosis, and its differentiation from sarcoidosis and lung cancer. DESIGN: The Ige against A60 and 38 kDa antigens in serum and BALF were measured using the commercially available IgG EIA kits. The study included 13 tuberculous patients, 8 patients with sarcoidosis, 10 patients with lung cancer and 9 healthy volunteers. RESULTS: In the serum studies the sensitivity of the assays did not exceed 40% and 60% in the estimation of IgG 38 kDa and Ige AGO, respectively. The specificity of both assays was similar: 81% (IgG 38 kDa) and 69-75% (Ige AGO). In BALF studies the sensitivity of the IgG 38 kDa assay was 50% and its specificity was 44%. The ranges of the IgG A60 concentrations in BALF were similar in all subject groups. CONCLUSION: In differentiation between tuberculosis, sarcoidosis and lung cancer, the measurement of IgG against A60 and 38 kDa antigens in serum is more useful than that in BALF.