Evaluation of Serological Tests Using A60 Antigen for Diagnosis of Tuberculosis

Identification of acid-fast bacilli (afb) in sputum or tissue samples is among definite diagnostic methods of tuberculosis. however, this method of diagnosis is restricted by certain limitations. serologic di-agnosis of tuberculosis (tb) has been used for a long time. the aim of this study was to determine the sensi-tivity and, specificity of antigen 60 (a60) igg, iga, igm test results in tb diagnosis. mycobacterial a60-based elisa was used to measure specific iga, igm and igg antibodies in the sera of 127 adult tb patients (consisted of 74 pulmonary and 53 extra-pulmonary cases), and 95 controls (46 healthy volunteers and 49 pa-tients with various acute or chronic diseases other than tuberculosis). data from a60 igg-based elisa, chest radiography, afb culture and pathologic evaluation for afb were obtained .the cutoff value of a60 igg, iga and igm were chosen according to a receiver operating characteristic (roc) analysis. the sensitivity, specificity and positive likelihood ratio were determined. the mean levels of igg, iga and igm were signifi-cantly higher in patients with pulmonary tuberculosis when compared with control groups. sensitivity of igg test was 54.3 %, while the specificity was 84.2%. the iga test showed a sensitivity of 70.1% with a specifici-ty of 80 %. combination of the igg and iga tests showed a total sensitivity of 45.7 % and a specificity of 94.7% and the positive likelihood ratio of 8.62. chosen cutoff values of igg, iga, and igm sets were 285,265 and 0.9 elisa units respectively. our study results showed a good specificity (94.7%) and a reason-able positive likelihood ratio (8.62) of the test when combined iga and igg with new cutoff points were con-sidered on diagnosis of tuberculosis in adult patients. combined use of both igg and iga tests results allows an increased accuracy in diagnostic of tuberculosis.