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Nonpeptidic antigens from the Mycobacterium tuberculosis cell wall are the focus of extensive studies to determine their potential role as protective antigens or serological markers of tuberculous disease. Regarding this latter role and using an enzyme-linked immunosorbent assay, we have made a comparative study of the immunoglobulin G (IgG), IgM, and IgA antibody responses to four trehalose-containing glycolipids purified from M. tuberculosis: diacyltrehaloses, triacyltrehaloses, cord factor, and sulfolipid I (SL-I). Sera from 92 tuberculosis patients (taken before starting antituberculosis treatment) and a wide group of control individuals (84 sera from healthy donors, including purified protein derivative-negative, -positive, healed, and vaccinated individuals, and 52 sera from nontuberculous pneumonia patients), all from Spain, were studied. The results indicated a significantly elevated IgG and IgA antibody response in tuberculosis patients, compared with controls, with all the antigens used. SL-I was the best antigen studied, showing test sensitivities and specificities for IgG of 81 and 77.6%, respectively, and of 66 and 87.5% for IgA. Using this antigen and combining IgA and IgG antibody detection, high test specificity was achieved (93.7%) with a sensitivity of 67.5%. Currently, it is widely accepted that it is not possible to achieve sensitivities above 80% in tuberculosis serodiagnosis when using one antigen alone. Thus, we conclude that SL-I, in combination with other antigenic molecules, could be a useful antigen for tuberculosis serodiagnosis.To control tuberculosis (TB), it is still necessary to find a diagnostic method that is both more rapid to carry out and more sensitive than traditional methods (smear and culture) but which is simpler and less expensive than the new molecular diagnostic tests that are based on the amplification of nucleic acids. Serological methods seem to be the ideal choice and, thus, many mycobacterial antigens have been evaluated: cellular extracts, proteins, and glycolipidic molecules from the mycobacterial cell wall (31). In addition to the lipoarabinomannan antigen, the acylated trehalose family has been the most frequently investigated group of glycolipids. They are 2,3-diacyltrehalose (DAT), 2,3,6-triacyltrehalose (TAT), 2,3,6,6Ј-tetraacyltrehalose 2Ј-sulfate (sulfolipid I [SL-I]), and trehalose-6,6Ј-dimycolate (cord factor [CF]). Using the enzyme-linked immunosorbent assay (ELISA) technique, several studies were performed with these antigens, and an extensive variability in immunoglobulin G (IgG) or IgM titers (6,7,11,18,20,(24)(25)(26) was obtained, i.e., test sensitivities were as different as 11 to 88% for the DAT antigen (11, 25) and 51 to 93% for the TAT antigen (11,26). These contradictory results are due to the ELISA protocol used (the different antigen concentrations or the use of detergent in washing buffers) (15, 30), or to the different sera groups analyzed (the number and type of patients and control subjects) (10). Thus, no definite conclusions as to th...

Although there is a universally enjoyed right to health care in Spain, some groups of TB patients could nevertheless be experiencing problems in seeking medical attention.

The humoral response to different proteinaceous antigens of Mycobacterium tuberculosis is heterogeneous among patients with active disease, and this has originated in the proposal to use a combination of several specific antigens to find an efficient serodiagnostic test for tuberculosis (TB) Serodiagnosis has been considered the Holy Grail of tuberculosis (TB) diagnosis research. A serological test would be the ideal method for implementation worldwide due to its low cost and simplicity. To replace the "gold standard," culture, a serological test should possess sensitivities of over 80% and test specificities of over.

Despite free health care being universally available in Spain, there are some groups of TB patients whose treatment is unduly delayed.

Homeless individuals have a very high risk of TB infection and disease and contact investigation requires specific methods for them. Programmes of screening and supervised treatment should be ensured in this group.

The high rates of TB among children and young adults suggest that TB transmission has increased during this period, especially among people at high risk of AIDS. The determinants of individual risk of TB among AIDS patients act together, especially in prisons. The HIV/TB coepidemic is an emerging threat potentially for all and requires expanding targeted measures to prevent and control both disease in our setting.