Diagnostic Significance of the Serologic Test Using Antigen of Mycobacterium Tuberculosis for Antibody Detection by ELISA

Park, Jae Min; Park, Yeon Soo; Chang, Yeon Soo; Kim, Young Sam; Ahn, Kang Hyun; Kim, Se Kyu; Chang, Joon; Kim, Sung Kyu; Lee, Won Young; Cho, Shang Rae

Abstract

BACKGROUND: Diagnosis by direct microscopy and/or by culture of the Mycobacterium tuberculosis from body fluids or biopsy specimens is "Gold standard". However, the sensitivity of direct microscopy after Ziehl-Neelsen staining is relatively low and culture of mycobacteria is time consuming. Detection of mycobacterial DNA in clinical samples by the polymerase chain reaction is highly sensitive but laborious and expensive. Therefore, rapid, sensitive and readily applicable new tests need to be developed. So we had evaluated the clinical significance of serologic detection of antibody to 38 kDa antigen, which is known as the most specific to the M. tuberculosis complex, and culture filtrate antigen by ELISA in sputum AFB smear negative patients. METHOD: In this study, culture tests for acid fast bacilli with sputa or bronchial washing fluids of 183 consecutive patients who were negative of sputum AFB smear were performed. Simultaneously serum antibodies to 38 kDa antigen and unheated culture filtrate of M. tuberculosis were detected by an ELISA method.
RESULTS
The optical densities of ELISA test with 38 kDa and culture filtrate antigen were significantly higher in active pulmonary tuberculosis cases than in non tuberculous pulmonary diseases (p<0.05), but in patients with active pulmonary tuberculosis, those of the sputum culture positive patients for M. tuberculosis were not significantly different from those of the sputum culture negative cases(p>O.05). In the smear-negative active pulmonary tuberculosis patients, the sensitivity of the ELISA using 38 kDa antigen and culture filtrate was 20.0% and 31.4%, respectively. The specificity was 95.3% and 93.9%, respectively.
CONCLUSION
In active pulmonary tuberculosis but smear negative, the serologic detection of antibody to 38 kDa antigen and culture filtrate by ELISA cannot substitute traditional diagnostic tests and does not have clinically significant role to differenciate the patient with active pulmonary tuberculosis from other with non-tuberculous pulmonary diseases.