Value of ELISA Using A60 Antigen in the Diagnosis of Active Pulmonary Tuberculosis

Abstract

This investigation was undertaken to assess the effectiveness of an enzyme-linked immunosorbent assay (ELISA) using A60 antigen in ascertaining diagnosis in hospitalized patients suspected to have pulmonary tuberculosis (TB) but with negative sputum stains. Cultures were performed to confirm active or inactive disease. IgG and IgM antibody activity was determined by adding a 1:100 dilution of serum to plates coated with A60 antigen. After addition of peroxidase-conjugated antihuman IgG or IgM and color development, optical density (OD) was determined. A total of 83 patients was studied, taking into account their current disease status and prior history. Using as a cutoff value the mean value +/- 2 SD measured in the negative culture, no TB history group, that is, OD = 0.50 for IgG measurements and 0.43 for IgM measurements, the sensitivity, specificity, and positive predictive value of IgG measurements were equal to 48, 71, and 50%, respectively. Using IgM measurements, these parameters were equal to 76, 98, and 95%, respectively. Combining the results of IgG and IgM measurements, sensitivity, specificity, and positive predictive value were equal to 68, 100, and 100%, respectively. Thus, the ELISA described here can greatly facilitate the diagnosis of TB in patients with negative smears.

ELISA METHOD FOR EVALUATION OF ANTI A60 lgG FOR THE DIAGNOSIS OF TUBERCULOSIS

“…9 These findings are more or less in the agreement with earlier reports. [10][11][12] In this study, specificity of the tests ranged from 66.6% to 80% in non-tuberculosis pulmonary pathology, but some patients analyzed departed strikingly from this norm and yielded different patterns of sero-positivity. Other authors have also reported similar events.…”

“…In the present study, relatively low seropositivity was seen in cases of sputum negative active pulmonary tuberculosis compared to those of sputum positive active pulmonary tuberculosis as shown in a previous study. 11 As far as serology in patients with extra pulmonary tuberculosis is concerned, a sensitivity of 47.3% for IgG was observed. The mean antibody levels were lower than the active pulmonary tuberculosis.…”

“…In studies carried out earlier, an IgG sensitivity ranging from 48-100% has been documented. 9,11,12 These wide variations could be due to different age groups studied, geographical area and severity of disease in different studies as well as variety in cut off limit used. In the present study, relatively low seropositivity was seen in cases of sputum negative active pulmonary tuberculosis compared to those of sputum positive active pulmonary tuberculosis as shown in a previous study.…”

Analysis of SEVA TB ES-31 antigen specific immunoglobulins IgM, IgA and IgG in sera of sputum and culture positive pulmonary tuberculosis

“…Gupta et alshowed sensitivity of 98.3% and specificity of 90% of combined IgG and IgA test using antigen A60 in adult pulmonary tuberculosis cases (5). AI Hajjaj et alshowed sensitivity of 87% and specificity of 95% for combined IgG and IgM estimation using A60 antigen (6), while Charpin et al showed sensitivity of 68% for combined lgG and IgM estimation (7). The wide variations in sen.sitivity of different combination of antibody types could be due to the different geographical areas, different antigen used, as well as severity of disease in different studies.…”

Evaluation of an In-House-Developed Radioassay Kit for Antibody Detection in Cases of Pulmonary Tuberculosis and Tuberculous Meningitis

“…The A60 antigen, which is a thermostable component of the purified protein derivative, has been used in the serodiagnosis of tuberculosis. In patients with smear-negative but culture-positive pulmonary tuberculosis, measurement of both IgM and IgG by ELISA revealed a sensitivity of 68% and a specificity of 100% (11). In the pediatric group, at a chosen specificity of 98%, anti-A60 IgG antibodies were observed in 68% of children with clinically active tuberculosis (15).…”