Serodiagnosis of tuberculosis. Evaluation of a sulpholipid antigen

In order to evaluate the suitability of serology in the diagnosis of tuberculosis the Mycobacterium tuberculosis anti-sulpholipidic IV IgG were assayed, using the ELISA test, in 41 healthy controls, 121 hospitalized but non-tuberculous patients and 142 tuberculous persons including 46 cured patients. At the 150 and 300 O.D. thresholds proposed in previous studies using the same antigen, the specificity was 88.27% and 98.76%, respectively, and the sensitivity 25% and 11.45%. These results were not related to different potential factors (age, background, associated pathology) but to infection intensity which enhanced the IgG reaction. This may explain discrepancies observed in previous studies made under other epidemiological conditions. Therefore, in this European population from a universitarity hospital, it appears that too many tuberculous patients have such a low IgG reaction that serology cannot be an effective assay in the diagnostic step.