The value of xpert MTB/RIF-generated CT values for predicting the smear status of patients with pulmonary tuberculosis

Abstract Background Smear microscopy is used to assess the patient's infectiousness at the time of initial diagnosis of pulmonary tuberculosis. However, its limited sensitivity and specificity highlights the need for new diagnostic strategies. The aim of our study was to assess the diagnostic accuracy of GX Ct value as a predictor of smear status and its usefulness to quantify mycobacterial load. Methods All GX-positive sputum samples during a seven-year period were included in the study. Correlations among Ct values, smear status and TTD on liquid culture were calculated. An optimal Ct value for ruling in infectious patients was established. Clinical and radiological variables were also analyzed. Results Sixty-eight samples from 65 patients were included. Ct value and TTD yielded a positive correlation ( ρ = 0.714; p