Egyptian Journal of Chest Disease and Tuberculosis (Jan 2020)
Evaluation of performance of quantiferon test in suspected pulmonary tuberculosis patients at Abbassia Chest Hospital
Abstract
Background Quantiferon (QFT) is an interferon-γ release assay applied to diagnose tuberculosis (TB). It is considered as an ELISA-based, whole-blood analysis as it uses peptides from three TB antigens (ESAT-6, CFP-10, and TB7.7) in an in-tube design. The conclusion is calculated as quantification of interferon (IFN-γ) in international units per ml. Positivity for Mycobacterium tuberculosis infection is when the IFN-γ response to TB antigens is beyond the cutoff. Aim Evaluation of performance of quantiferon test of suspected pulmonary TB patients at Abbassia Chest Hospital and a trial to set a cutoff point of quantiferon test if possible. Patients and methods This study was a prospective, randomized study conducted on 100 cases with suspicion of pulmonary TB at Abbassia Chest Hospital, during the period from January 2015 to December 2016. All cases were subjected to: history taking (present, past, and family), examination (general, local chest), chest radiograph (posteroanterior view), sputum for acid fast bacilli (by Ziehl Neelsen stain), and quantiferon test. Results Quantiferon test results were (54) 54% negative and (46) 46% positive. Tuberculin skin test was done only for 17 cases of the studied group with (7) 41.2% being negative and (10) 58.8% being positive. There was no statistically significant relation found between TB AG-nil and quantiferon test results and demographic data of the studied patients. There was statistically significant higher incidence of sweating, fever, loss of weight, loss of appetite, and productive cough in patients with increase in the level of TB AG-nil and positive quantiferon test results, increase in the incidence of multiple cavitary lesions in patients with increase in the level of TB AG-nil and positive quantiferon, significant increase in the incidence of positive sputum for acid fast bacilli patients with increase in the level of TB AG-nil and positive quantiferon group. The receiver operating characteristic curve shows that the best cutoff point to predict patients with positive quantiferon test was found to be more than 0.33, with a sensitivity of 100% and specificity of 93.55%, and area under the curve of 96.8%. Conclusion Quantiferon test is a useful investigation in suspect pulmonary TB patients, especially if used in combination with other investigations, full history, and examination.
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