The Whole Blood Interferon Gamma Release Assay In The Diagnosis Of Smear Negative Tuberculosis And Tuberculous Pleurisy

Purpose: The study aimed to ascertain in routine clinical practice the accuracy of a whole blood interferon gamma assay for the diagnosis and differentiated diagnosis of smear negative tuberculosis and tuberculous pleurisy.Methods:243 participants were enrolled in this study, including 35 healthy control, 106 patients with clinical diagnosed tuberculosis(44 patients with microscopy or culture confirmed tuberculosis without treatment, 47 patients with smear negative tuberculosis, 15 patients with self-cured tuberculosis ), 37 patients with tuberculous pleurisy, 43 patients with pathological confirmed lung cancer, 13 patients with non-tuberculosis pulmonary dieases and 32 patients with malignant pleural effusion.The test is performed by obtaining whole heparinazed blood incubating it with purified protein derivative(PPD) and specific M. tuberculosis antigen early secretory antigenic target 6(ESAT-6) and ESAT-6/CFP-10 fusion protein encoded in the mycobacterial genomic region of difference (RD) 1, after 16-22 hours, the production of IFN-γis measured by ELISA. Other antigens, such as phytohemaglutin and saline, are used as positive and negative controls. The test is reported as positive, negative and indeterminate.Result: 1 The production of IFN-γstimulated by ESAT-6, ESAT-6/CFP-10 and PPD in active tuberculosis and tuberculous pleurisy is much higher than the production in healthy control(p<0.01). 2 The patients who had accumulated infiltration over 4 segments on the X-ray have lower production of IFN-γcomparing to the patients not more than 4 segments(p<0.05), as well as the patients who had a lower peripheral blood lymphocyte count(<1.0×109)( p<0.01);In the self-cured tuberculosis cases, the production of IFN-γis lower than the production in smear positive tuberculosis stimulated by ESAT-6/CFP-10 and PPD(p< 0.01), and in the smear negative tuberculosis stimulated by PPD(p<0.05);As for other clinical influenced factors, such as age, diabetes, cavity, load of bacillus, there are no significant differences can be seen in this study(p>0.05).3 The production of IFN-γstimulated by ESAT-6, ESAT-6/CFP-10 and PPD in smear negative tuberculosis is much higher than the production in the patients with lung cancer and non-tuberculosis pulmonary dieases(p<0.01), as well as the tuberculous pleurisy higher than the malignant pleural effusion(p<0.01).4 If we take 31pg/ml(ESAT-6),1458pg/ml(ESAT-6/CFP-10),2068pg/ml(PPD) as the cut-off value based on a ROC curve, the positive rate in active tuberculosis and tuberculous pleurisy is higher than the rate in the healthy control(p<0.01); Except for PPD, the positive rate stimulated by ESAT-6 and ESAT-6/CFP-10 in smear negative tuberculosis and tuberculous pleurisy is higher than the rate in the patients with lung cancer and non-tuberculosis pulmonary dieases(p<0.01) and the patients with malignant pleural effusion(p<0.01);besides,there is no significant defference in the positive rate between smear positive tuberculosis and smear negative tuberculosis(p>0.05).5 If we chose anyone positive of ESAT-6 or ESAT-6/CFP-10 as the criterion, the whole blood interferon gamma release assay has the 83.0% for sensitivity, 74.3% for specificity and 79.3% for accuracy in the diagnosis of smear negative tuberculosis, and 78.4%, 74.3%,76.4% in tuberculous pleurisy. It is similar to the LAM but higher than the ADA. Combine the LAM can improve the sensitivity in smear negative tuberculosis to 93.6% and 86.5% in tuberculous pleurisy.Conclusion: The whole blood interferon gamma release assay is a useful tool for the diagnosis and differentiated diagnosis in smear negative tuberculosis, and the differentiated diagnosis in tuberculous pleurisy. Anyone positive of ESAT-6 or ESAT-6/CFP-10 should be chosed as the criterion. Combine the LAM can improve the sensitivity and accuracy in smear negative tuberculosis and tuberculous pleurisy. We suggest that the whole blood interferon gamma release assay could be a very useful supplementary tool for the diagnosis of the smear negative tuberculosis and tuberculous pleurisy.