Diagnosis of Tuberculosis by Using Enzyme-Linked Immunosorbent Assay (ELISA) to Detect Anti-Mycobacterial Superoxide Dismutase Antibodies in The Patients

Tuberculosis (TB) is an ancient human scourge that continues to be an important public health problem worldwide. The risk of increasing spread of tuberculosis and development of drug resistance make early diagnosis a matter of utmost concern. Improved rapid methods for laboratory confirmation are therefore urgently required.
Superoxide dismutase (SOD), an important secretory protein of Mycobacterium tuberculosis, has been ignored in the past for the development of a serodiagnostic test. We have evaluated the performance of an ELISA based on the detection of antibody to SOD in TB patients.
The presence of antibodies to SOD has been detected in most TB patients' sera. TB sera exhibited 93-94% positivity and showed a significantly higher response (p<0.0001) when compared with the serum samples from The Regional Blood Transfusion Centre. A slightly lower positive predictive value (77%) was obtained when Indian TB cases were compared with Indian normals. Similarly, an 88% positive predictive value was obtained with Egyptian TB cases. This test showed a significant level of specific response (p<0.0001). 25% of The Indian normals also found to contain a high level of antibodies to mycobacterial SOD. This may be due to the prevalence of M. tuberculosis or other mycobacteria in the environment or they may be early TB cases.
The test has a 98% specificity with 93-94% positive predictive value. However this is preliminary data and its performance needs to be evaluated on larger numbers of confirmed positive TB patients and controls.