A60 Antigen Research Articles

Evaluation of IgG, IgA and IgM against Mycobacterial Antigen in Patients with Extrapulmonary Tuberculosis

Tuberculosis (TB) is a specific infectious disease usually caused by the tubercle bacillus, Mycobacterium tuberculosis (MBT). It primarily affects the lungs and causes pulmonary tuberculosis (PTB) and when it affects other organs it is known as extrapulmonary tuberculosis (EPTB). The diagnosis of TB largely depends on case history, clinical examination, radiological finding and subsequent laboratory confirmation by bacteriological examination. But the radiological findings are not specific and the sensitivity of AFB (acid fast bacilli) smear is poor. To overcome this difficulty, various serological tests have been tried. A novel antigen namely A60 antigen was found to be highly immunogenic and this present study was carried out to see the diagnostic significance of the ELISA test for A60 antigen in diagnosing extrapulmonary tuberculosis. The study was designed as a cross-sectional study involving both extrapulmonary TB patients and controls. Their serum immunoglobulins (IgG, IgA and IgM) specific toA60 antigen were measured by enzyme linked immunosorbent assay (ELISA) technique. In this study, IgG, IgA and IgM was significantly elevated among the EPTB patients as compared to the controls and the IgA and IgM ELISA test combinations was most ideal in diagnosing EPTB. Keywords: Tuberculosis, Extrapulmonary tuberculosis, AFB (acid fast bacilli), A60 antigen, ELISA (enzyme linked immunosorbent assay), Immunoglobulin.

Evaluation of Antigen Detection Test (Chromatographic Immunoassay): Potential to Replace the Antibody Assay Using Purified 45‐kDa Protein for Rapid Diagnosis of Tuberculosis

The current strategy for combating tuberculosis (TB) is based on the early detection and treatment of patients to halt transmission. The present study was conducted to evaluate the diagnostic potential of three Mycobacterium tuberculosis antigens, 45-kDa, A60, and sonicated MTB antigen (SmTB-Ag), as antibody/antigen detection methods for the rapid and accurate diagnosis of TB. The SmTB-Ag and 45-kDa antigens were purified and A60 antigen was supplied by Anda-Biologicals, France. The 45-kDa and A60 antigens (for antibody detection procedures) and SmTB-Ag (for antigen detection test) were tested in the same study subjects. ELISA and immunochromatographic (rapid) test were performed on 201 sputum and serum samples. Ninety-eight samples from TB patients and 103 samples from control individuals were studied. The mean absorbance value of antibodies against 45-kDa antigen in the TB patients were (1.17 ± 0.44, CI 1.09-1.26), significantly higher than in the non-TB group, (0.8± 0.28, CI 0.74-0.85, P< 0.05). The sensitivities of tests using two antigens, 84% for the 45-kDa antigen and 65% for the A60 antigen, were lower than SmTB-Ag(93%). The rapid test yielded 93% sensitivity and 92% specificity. Findings highlighted the importance of antigen detection as a diagnostic tool. The rapid test evaluated in this study may be useful for diagnosis of TB.

Choosing the right SSC

BACKGROUND Diagnosis of extrapulmonary tuberculosis is often difficult to establish using standard methods. Serological techniques based on detection of antibodies against mycobacterial antigen A60 have shown good sensitivity and specificity in pulmonary tuberculosis. The present study was undertaken to define the diagnostic accuracy of testing for IgG and IgA against A60 in extrapulmonary tuberculosis. METHODS One hundred and ninety eight subjects were studied: 42 patients with extrapulmonary tuberculosis confirmed by microbiology and/or histology, 24 subjects with healed pulmonary or extrapulmonary tuberculosis, 44 patients with a defined non-tuberculous disease, and 88 healthy volunteers (44 PPD negative and 44 PPD positive). Detection of IgG and IgA against A60 antigen was carried out by enzyme-linked immunosorbent assay. Cut off values were determined by receiver operating characteristic curves. RESULTS Sensitivity of the IgG test was 73.8% in extrapulmonary tuberculosis, while the specificity was 96.1%. The IgA test showed a sensitivity of 69.0% with a specificity of 93.6%. Combination of the IgG and IgA tests showed a sensitivity of 80.9% and a specificity of 92.3%. Patients with extrapulmonary tuberculosis showed significantly higher titres of both IgG and IgA against A60 than other groups. CONCLUSIONS Anti-A60 IgG or IgA tests are characterised by good sensitivity and specificity. The combined use of both tests allows an increase in diagnostic accuracy of extrapulmonary tuberculosis.

Purification of modified mycobacterial A60 antigen by affinity chromatography and its use for rapid diagnostic tuberculosis infection

Tuberculosis has been declared a global emergency. The mainstay for its control is the rapid and accurate identification of infected individual. Antibodies to A60, one of the macromolecular antigen complexes of mycobacteria were commonly used in the rapid detection of Mycobacterium tuberculosis. The aim of this study was to prepare specific antibodies against A60 for detection of tuberculosis infection. Specific polyclonal antibodies against A60, (A60-Ab) were prepared in rabbits using 2 boosted injections of the antigen (A60). The antibodies were purified and treated with normal oral flora to remove any non-specific and cross-reactive antibodies. These antibodies were conjugated to CNBr-activated Sepharose 4B and used to isolate subunits of A60 with more specificity for M. tuberculosis. A new affinity column was designed to prepare modified (purified) A60 antigen. Purified A60 antigen (PA60-Ag) was used to develop antibody production by Immunoaffinity chromatography. 113 patients with a confirmed diagnosis of pulmonary TB at Pasteur Institute were selected for the study. The specificity of the results was analyzed with TB-rapid test by using PA60-antibodies. TB-rapid test revealed that normal oral flora-absorbed antibodies could lead to more specific results than that of the non-absorbed antibodies. The developed, modified A60 antibodies, (PA60-Ab)-rapid test showed higher sensitivity, specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV) and overall efficiency (93.0%, 86.0%, 90.0%, 91.0%, and 90.0% respectively) for the detection of the Mycobacterium antigen. Moreover, PA60-Ag showed only two protein bands of molecular weight 45 and 66kDa in SDS-PAGE while untreated A60 showed multiple bands. Thus, our study helped in the purification of a novel and well characterized A60 antigen and good diagnostic potential for detecting tuberculosis infection.

Evaluation of the diagnostic value of measuring IgG, IgM, and IgA antibodies to mycobacterial A60 antigen in active tuberculosis

The purpose of the present study was to evaluate the clinical usefulness of detection of serum immunoglobulin A (IgA), IgG, and IgM antibodies raised against the mycobacterial A60 antigen for the diagnosis and discrimination of active tuberculosis (TB) from other pulmonary diseases. Three commercially available ELISA kits (IgA, IgG, and IgM) (ANDA Biologicals, Strasbourg, France) were evaluated simultaneously in 246 serum samples from 3 groups of patients: group I, 171 patients with active TB (128 pulmonary TB and 43 extrapulmonary TB); group II, 73 patients with pulmonary non-TB diseases; and group III, 2 leprosies patients. The sensitivities of tests ranged from 31.3% (IgA) to 94% (IgG) in pulmonary TB patients and from 21% (IgA) to 84% (IgG) in extrapulmonary TB patients. The specificities of assays varied from 92% (IgG) to 96% (IgA) in the pulmonary non-TB group. Combination of IgG with IgA and/or IgM does not improve its sensitivity. Clinical use of the A60-based serodiagnostic IgG assay is of great value for the rapid diagnosis and discrimination between active TB and pulmonary non-TB diseases. Moreover, this test could be used to increase diagnostic accuracy, especially for smear-negative TB cases, which are difficult to diagnose.

A Novel Monoclonal Antibody Against A60 Antigen ofMycobacterium bovisBacillus Calmette-Guerin

Mycobacterium contains several immunologically active substances, which play a principal role in mycobacterial diseases. The majority of the highly antigenic proteins present in mycobacterial homogenates are components of the A60 complex. In this study, A60 antigen was prepared from cytoplasm of Mycobacterium bovis Bacillus Calmette-Guerin (BCG). Cytoplasm was fractionated by passage through the column of sepharose 6B and ConA-sepharose 4B. After purification of spleen cells of the immunized mice, the cells were fused with SP2/0 myeloma cells. Four clone cell lines producing antibody against A60 antigens were established and each clone was tested for immunoreactivity against purified A60 by ELISA and immunoblotting. The clone designated DEB7 reacted strongly with A60. Immunoblotting using MAb DEB7 showed that this MAb binds to a single protein of A60 subunit with a molecular weight of 65 kDa. This subunit of A60 M. bovis recognized by DEB7 MAb could be used to increase the sensitivity and specificity of immunoassay or other potential roles in mycobacterium infection.

Immunization of mice with the antigen A60 of Mycobacterium bovis BCG.

Antigen 60 (A60) is a thermostable component of the cytoplasm of Mycobacterium tuberculosis and BCG which can be fractionated into at least 15 protein bands when analysed by Western blot. Normal B6D2 mice were immunized subcutaneously with 20 micrograms of the A60 protein suspended in Freund's incomplete adjuvant (FIA) or in saline. Three weeks later the mice received a second dose of vaccine followed 2 weeks later by an aerogenic challenge with approximately 10(3) CFU of M. tuberculosis Erdman. The mice receiving the adjuvanted A60 showed a significant reduction (P less than 0.05) in the number of viable organisms recovered from the lungs and the spleen 3 weeks after challenge. However, this response was less than that seen in BCG vaccinated controls.

Evaluation of anti-A60 antigen IgG enzyme-linked immunosorbent assay for serodiagnosis of pulmonary tuberculosis.

BACKGROUND:Problems in the diagnosis of tuberculosis using smear and culture techniques have necessitated the exploration of the utility of serodiagnosis to support clinical suspicion of tuberculosis. Anti-A60 antigen IgG enzyme-linked immunosorbent assay (ELISA) was evaluated as a tool for the diagnosis of active pulmonary tuberculosis.MATERIALS AND METHODS:ELISA was used for the detection of immunoglobulin G (IgG) against A60 antigen in parallel with other familiar diagnostic methods in 70 patients with pulmonary tuberculosis (Group_I) along with 70 controls showing evidence of latent tuberculosis infection (Group II).RESULTS:ELISA results were positive in 63 (90%) patients in Group_I compared to three (4%) controls in Group_II. Group_I patients had significantly higher titers of IgG (mean = 750.79 ± 115.87 U/ml against the A60 antigen as compared to Group II controls (mean = 206.67 ± 20.81 U/ml (P < 0.0001). The overall sensitivity and specificity obtained using ELISA were 90 and 95.7% respectively in active pulmonary tuberculosis. Ziehl-Nielsen (Z-N) stains for acid-fast bacilli were positive in 60 (85.7%) patients. In 48 (68.6%) patients, M. tuberculosis grew on both Lowenstein-Jensen (L-J) medium and BACTEC MGIT 960 liquid medium with mean detection times of 45 and 8 days respectively. Tuberculin skin test was positive in 38 (54.3%) patients. Chest X-ray results were consistent with the diagnosis of pulmonary tuberculosis in 53 (75.7%) patients.CONCLUSION:Anti-A60 IgG ELISA results were significantly positive and associated with elevated antibody titers in pulmonary tuberculosis as compared to latent mycobacterium infection. The high diagnostic performance of the test makes it a useful, simple and rapid supporting tool to validate clinical suspicion of active pulmonary disease.

Measurement of Immunoglobulin G against Mycobacterial Antigen A60 in Patients with Cystic Fibrosis and Lung Infection Due to Mycobacterium abscessus

The diagnosis and prognosis of lung infections due to the emerging nontuberculous mycobacterium (NTM) Mycobacterium abscessus are difficult to establish in children with cystic fibrosis. We evaluated the usefulness of an enzyme-linked immunosorbent assay for detecting serum IgG antibodies against the ubiquitous mycobacterial antigen A60. A total of 186 patients with cystic fibrosis (mean age+/-SD, 12.0+/-5.0 years) were studied, including 15 M. abscessus-positive patients who fulfilled American Thoracic Society (ATS) criteria for NTM infection (M. abscessus-infected patients), 7 M. abscessus-positive patients who did not fulfill ATS criteria, 20 patients positive for various other NTM who did not fulfill ATS criteria, and 144 NTM-negative control patients; mean IgG titers (+/-SD) for these 4 groups were 718+/-342 U, 193+/-113 U, 129+/-49 U, and 121+/-53 U, respectively (M. abscessus-infected patients vs. each of the other groups, P<.005). The A60 IgG test was both sensitive (approximately 87%) and specific (approximately 95%) if adapted cutoff values were used (150 U and 250 U for patients aged <or=10 years and patients aged >10 years, respectively) and correlated well with results of acid-fast bacilli smears. Measurement of anti-A60 IgG may be useful for both the diagnosis and assessment of activity of M. abscessus lung infection in persons with cystic fibrosis.

Serodiagnosis of tuberculosis using two ELISA systems.

Serodiagnosis by ELISA has been widely explored over the years, in the diagnosis of tuberculosis. Two ELISA systems were evaluated for detection of mycobacterial antibodies in pulmonary and extra pulmonary tuberculosis. The two test assays explored were ERBA LISA (TB IgG) test (Anda Biologicals) which uses A60 antigen complex found in the cytosol of typical and atypical mycobacteria, and SEVA TB (IgG) ELISA, which uses a 31 kDa, glycoprotein antigen purified fromM. tb H(37)Ra culture filtrate. Sera from 98 proven tuberculosis [pulmonary TB (48), tuberculous lymphadenopathy (30), tuberculous meningitis (15) & genitourinary TB (5)] were studied along with 32 healthy controls. The overall positivity obtained using ERBA LISA (TB IgG) test and SEVA TB (IgG) ELISA test was 72.9% and 91.6% in pulmonary tuberculosis, 43.3% and 76.6% in tuberculous lymphadenopathy respectively. The sensitivity of ERBA LISA test in tuberculous meningitis and genito-urinary TB was significantly low (26.6% & 40% respectively) compared to sensitivity obtained using SEVA TB ELISA (86.6% & 60% respectively) with overall specificity of 60% and 87.5%. Thus SEVA TB IgG ELISA test was found to be more sensitive than ERBA LISA in detecting IgG antibodies in tuberculous sera, in particular in extra pulmonary tuberculosis cases.

The value of pleural fluid anti-A60 IgM in BCG-vaccinated tuberculous pleurisy patients

Objectives To determine if detection of IgM and IgG antibodies against mycobacterial antigen A60, together with the Mantoux tuberculin skin test (TST), could be used in the diagnosis of tuberculous pleurisy (TP) in BCG-vaccinated cases.Methods We investigated 125 BCG-vaccinated patients with pleural effusion. Of these, 88 had TP and 37 had non-tuberculous pleurisy (NTP). TST and anti-A60 IgM and IgG measurements by ELISA were performed in the sera and pleural effusions of both groups.Results Cut-off values, in optical density, for serum anti-A60 IgM, pleural fluid anti-A60 IgM, serum anti-A60 IgG and pleural fluid anti-A60 IgG were defined as 0.624, 0.614, 0.464, and 0.613, respectively. TP patients had higher IgG and IgM levels in the serum (P < 0.001 and P < 0.05, respectively) and pleural effusion (P < 0.001 and P < 0.001, respectively). Regardless of the diagnosis, IgG and IgM levels were higher in the sera (P < 0.001 and P < 0.05, respectively) and pleural effusions (P < 0.001 and P < 0.001, respectively) of TST-positive cases, and serum and pleural fluid IgM levels were higher (P < 0.001 and P < 0.001, respectively) in the TST-positive TP cases. Sensitivity and specificity of TST were 65% and 68%, respectively. As a single parameter, pleural fluid anti-A60 IgM had the highest sensitivity (77%) and specificity (94%) in patients with negative TST.Conclusion We suggest that in populations where tuberculosis prevalence is high and BCG vaccination is common, pleural fluid anti-A60 IgM can facilitate the diagnosis of TP.

The magnitude of the immune response to heat shock protein-65 following BCG immunisation is associated with the extent of experimental atherosclerosis

Several studies have reported associations between coronary heart disease (CHD) and infection. Recent studies have implicated immune responses to heat shock protein(s) (HSP) as a contributary factor. Using an immunisation model, we have assessed the relationship between the immune responses to HSP and subsequent atherosclerosis. Rabbits were immunised with bacillus Calmette–Guerin (BCG) vaccine ( n=10) or saline ( n=10) and subsequently fed a 0.25–1.0% cholesterol diet for 10 weeks. Plasma levels of IgG specific for mycobacterial antigen A60 and human HSP-60, but not for human HSP-70, rose following BCG immunisation, reaching a peak after 8 weeks. The percentage aortic area covered by atherosclerotic plaque was greater in animals immunised with BCG (30.5±3.8) compared to saline treated animals (16.4±2.6) ( P<0.05). Furthermore, the individual titres of anti-HSP-60 in the BCG-immunised animal antibodies at week 8 (prior to starting the cholesterol diet) correlated with the percentage aortic area covered by plaque after 18 weeks ( R 2=0.72; P<0.05). No correlation was found between anti-A60 antibody titres and plaque area. Antiserum from BCG-immunised, but not control, animals stained heat-shocked endothelial cells. These data suggest that immune responses to HSP may be implicated in the relationship between specific infections and CHD.

Serodiagnosis of tuberculosis by enzyme immunoassay using A60 antigen

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Nontuberculous mycobacteria in patients with cystic fibrosis.

The prevalence and clinical implications of colonization with nontuberculous mycobacteria were prospectively studied in 37 patients who had cystic fibrosis. Sputum samples were cultured on Coletsos and Löwenstein-Jensen selective media after decontamination with sodium hydroxide and oxalic acid. Oxalic acid-decontaminated fractions were also cultured in selective liquid medium. Nontuberculous mycobacteria were isolated from 6 patients (16.1%). Mycobacterium chelonae and Mycobacterium avium-intracellulare complex were the most common species. Three patients with positive results of culture had at least 1 positive result by acid-fast smear. Oxalic acid decontamination and culture in liquid medium had the lowest contamination rate (6.7%). Colonization with nontuberculous mycobacteria was associated with humoral response to mycobacteria (immunoglobulin G titers against antigen A60) in patients with samples that tested positive by acid-fast smear. An improvement in pulmonary function was observed in 2 patients after they received a course of antimycobacterial therapy. Screening for nontuberculous mycobacteria in patients with cystic fibrosis will contribute to understanding the relevance of these pathogens with regard to deterioration of pulmonary function in patients with cystic fibrosis.

Tuberculosis antigen A60 serodiagnosis in tuberculous infection: Application in extrapulmonary and smear‐negative pulmonary tuberculosis

An ELISA diagnostic test for tuberculosis antigen A60 (TBA60) IgG/IgM was used in a tertiary referral hospital in Taiwan. From June 1992 to December 1993, serum samples obtained from 907 patients were analyzed for TBA60 IgG and IgM titres. The final diagnosis of these patients was confirmed by microbiological study and clinical follow up for 18-24 months. Among 147 patients with active pulmonary tuberculosis, IgG was positive in 112 (76.2%), IgM was positive in 14 (9.52%). Among 90 patients with active extrapulmonary tuberculosis, IgG was positive in 53 (58.9%), IgM was positive in 9 (10%). Among 153 patients with inactive tuberculosis, IgG was positive in 28 (18.3%), IgM was positive in 1 (1.6%). Among 517 patients with nontuberculous disease, IgG was positive in 50 (9.7%), IgM was positive in 3 (0.6%). In this study population with 26% (237/907) active tuberculous infection rate, the TBA60 ELISA IgG had a diagnostic sensitivity of 69.6% and a specificity of 92.1%. These results indicate a positive predictive value of 67.9% and a negative predictive value of 89.2%. The sensitivity of IgM was 10.5% and specificity, 99.4%. The serum IgG tire had good correlation with the extent of pulmonary TB had a higher percentage of IgG seropositivity (83.9%) than those with smear-negative pulmonary TB (70.6%) and extrapulmonary TB (58.9%). In 50 cases with active tuberculosis, follow-up examinations were carried out one month after treatment. In 18 cases with initially negative IgG and IgM titres, 13 showed elevation of serum IgG titres into positive level, one had positive seroconversion of IgM which was the only serological marker indicating active infection. Therefore, 77.8% (14/18) gained diagnostic benefit from follow-up serological examination. It was concluded that TBA60 IgG and IgM ELISA is a useful test when diagnosing tuberculosis. This test also assists in the clinical judgement of tuberculosis when used as an adjunct to symptoms and sputum smear, and for monitoring therapeutic response at the commencement of treatment.

Evaluation of a western blot serum test for the diagnosis of Mycobacterium tuberculosis infection.

This study was designed to evaluate the possibility of monitoring Mycobacterium tuberculosis infection using a serological assay. A discriminant score comprising antigen fractions of 38, 28, 24 and 19 kDa, identified in western blots using the Mycobacterium bovis bacille Calmette-Guérin (BCG) A60 antigen complex was established in a sample of 57 purified protein derivative (PPD)-negative and 47 PPD-positive individuals. It was then tested in a group of 140 subjects undergoing BCG vaccination as a model of tuberculosis complex infection and in a group of human immunodeficiency virus (HIV)-infected individuals as a model of cell-mediated immunodeficiency-related risk of tuberculosis. The discriminant score identified 57 out of 57 (100%) PPD-positives and none (0%) of the 47 PPD-negatives. In the BCG vaccinated subjects, 1.4% tested positive before vaccination and 90% after vaccination. In the HIV-positive subjects, 90% of the PPD-positive and 5% of the PPD-negative subjects had a positive score. This study suggests that the western blot discriminant score is an accurate test to survey M. tuberculosis infection in serum samples.

54 P - A60-Elisa test in diagnosing of lung tumours

A60-ELISA test is a new valuable tool in diagnosis of pulmonary tuberculosis (PTB). The aim of the present study was to define if this test might be useful in differentiating PTB from lung cancer (LC). The levels of IgG antibodies against A60 antigen of r1ycobacterium bovis BOG was measured by ELISA test with the use IMMUNO kit. 117 subjects were enrolled into the study: 58 healthy controls (Group I), 18 patients with defined diagnosis of LC (Group II), 15 with lung tumour, without histologic diagnosis (Group III) and 26 with nonmalignant and nontuberculous lung diseases (Group IV). By using 200 Uj/ml as a cut-off point, the test was positive in 2/58 subjects from Group I, 0/18 from Group II, 2/15 from Group III and 2/26 from Group IV. For both patients from Group III having a positive result of the test PTB was suspected, but to exclude LC thoracotomy was performed and the diagnosis of PTB was histologically confirmed. We conclude that A60-ELISA test might be useful tool in the differential diagnosis of LC.

IgA immune response against the mycobacterial antigen A60 in patients with active pulmonary tuberculosis.

Searching for IgG and IgM against the mycobacterial antigen A60 has been recognized as a potential diagnostic tool for pulmonary tuberculosis. The role of detection of anti-A60 IgA in improving diagnostic accuracy of serology is not well known. In this study we measured with ELISA serum levels of both anti-A60 IgG and IgA in 216 subjects. 88 healthy volunteers (44 PPD- and 44 PPD+), 44 patients suffering from nontuberculous lung disease and 15 subjects with healed pulmonary tuberculosis constituted the control population; 69 patients with active pulmonary tuberculosis (35 cavitary forms, 26 productive forms and 8 miliary forms) were examined. The sensitivity of IgG test was 73.9% in pulmonary tuberculosis (77.1% in cavitary forms, 65.4% in productive forms, 87.5% in miliary forms); the specificity of the test was 95.9%. For the IgA test we observed a sensitivity of 72.5% (74.3 in cavitary forms, 69.2% in productive forms, 75.0 in miliary forms) and a specificity of 93.9%. Combination of the two tests increased the sensitivity to 84.0% (+10.1% compared to IgG test, +11.5% compared to IgA test); the specificity decreased to 92.5% (-3.4% vs. IgG test; -1.4 vs. IgA test). In conclusion, the combined use of evaluation of anti-A60 IgG and IgA increases the accuracy of serological diagnosis of pulmonary tuberculosis.

391-PA10 Humoral immune response against A60 antigen in diagnosis of tuberculosis

391-PA10 Humoral immune response against A60 antigen in diagnosis of tuberculosis

Diagnostic utility of the estimation of mycobacterial Antigen A60 specific immunoglobulins IgM, IgA and IgG in the sera of cases of adult human tuberculosis

Setting: An ELISA assay based on mycobacterial Antigen A60 for the estimation of Mycobacterium-specific immunoglobulins in the serum has been used successfully for the rapid diagnosis of tuberculosis in studies done in the Western countries. There are hardly any similar large scale studies in India. Objective: To evaluate the utility of this ELISA test for rapid diagnosis of different clinical forms of tuberculosis in an adult Indian population. Design: ELISA test based on mycobacterial antigen A60 (Anda Biologicals, France) was used to estimate specific IgM, IgA and IgG antibodies in the sera obtained from 337 cases of tuberculosis and 131 controls in the population of Delhi (India). Results: Of the 131 controls, only 9.9% were positive for IgM, 7.6% for IgG, 6.1% for IgA and 9.9% when an IgA and IgG combination was considered. Of 122 cases of active pulmonary tuberculosis, 41% were positive for IgM, 86.8% for IgA, 88.5% for IgG and a very high positivity (98.3%) was seen when IgA and IgG estimations were combined. A relatively low seropositivity was observed in 25 cases of pleural tuberculosis. The corresponding figures in 130 cases of extrapulmonary tuberculosis were 22.3%, 68.4%, 73.8% and 86.15%. When 60 cases of pulmonary tuberculosis who had been successfully treated with antituberculosis drugs were analyzed the rates of seropositivity fell to 11.6%, 46.6%, 58.3% and 66.6% respectively. Conclusion: Our findings point to a very good sensitivity (91.6%) and specificity (90.0%) of the test when combined IgA and IgG antibody titres are considered, to detect cases of adult tuberculosis. The role of IgM estimation can be restricted to the detection of cases of reactivation of tuberculosis.