Pathozyme-Myco G (Myco G), M, A, and TB complex plus (Omega Diagnostics Ltd., Alloa, Scotland) were evaluated for the serological diagnosis of pulmonary tuberculosis (TB) in an Argentinean population. Sera from 58 patients with pulmonary TB, 24 subjects with pulmonary mycobacteriosis or mycoses (pulmonary MM group), and 45 subjects with other underlying disorders (control group) were analyzed. The sensitivities of the tests ranged from 29% (Myco M) to 82% (Myco G) in smear-positive patients (17 subjects) and from 29% (TB complex plus) to 49% (Myco G) in smear-negative patients (41 subjects). The specificities of the assays varied from 93% (Myco M) to 100% (Myco G and TB complex plus) in controls and from 62% (Myco A) to 96% (TB complex plus) in the pulmonary MM group. Overall, for the diagnosis of smear-negative patients, Myco G had the best characteristics, with a sensitivity of 49% and specificities of 100% for controls and 75% for the pulmonary MM group; after its combination with TB complex plus, its sensitivity improved to 59%. Nevertheless, despite its relatively poor capacity to discriminate between pulmonary TB and pulmonary MM, Myco G, alone or in combination with TB complex plus, would be a useful diagnostic tool for patients with suspected pulmonary TB living in areas where the relative prevalence of pulmonary MM was low.Several enzyme-linked immunosorbent assays (ELISAs) have been tried to achieve the rapid, early, and easy diagnosis of pulmonary tuberculosis (TB) (4, 5). However, a large variability in their accuracy has been reported depending on the antigen employed, the immunoglobulin (Ig) class measured, the strain variation, and the deviation in the antibody response among different ethnic groups (4). The evaluation of different serological kits at the same time with the same group of sera has been rarely carried out (4,6,17). This study was conducted to evaluate the potential of four ELISA kits: Pathozyme-TB complex plus (TB complex plus), Pathozyme-Myco G (Myco G), Myco M, and Myco A (Omega Diagnostics Ltd., Alloa, Scotland) for pulmonary TB diagnosis. The first kit detects IgG antibodies against recombinant forms of two antigens from the Mycobacterium tuberculosis complex: r38 kDa (PstS-1, PhoS, antigen 5, antigen 78 [1]), expressed in and purified from Escherichia coli (20), and r16 kDa, a member of the alphacrystalline family of low-molecular-weight heat shock proteins (23). The details regarding the method for producing r16 kDa antigen are considered proprietary by the manufacturer and are unknown to the authors. Both antigens have been considered species-specific antigens of the M. tuberculosis complex (14, 23). The other tests, which utilize the r38 kDa antigen and the lipoarabinomannan (LAM; a common lipoglycan component of the mycobacterial cell wall [7]) purified from M. tuberculosis (13), detect human IgG, IgM, or IgA, respectively, in response to infection with mycobacterial species. Sera and sputum samples were obtained from ambulatory patients with suspected but not proven pulmon...