Comparison of Quantitative Relationship between Real-Time PCR and Acid Fast Bacilli Staining for Diagnosis of Pulmonary Tuberculosis

Abstract

This study investigates the association of the AFB stain with the cycle threshold (Ct) value of the Cobas TaqMan MTB test (CTM test, Roche Diagnostics, Basel, Switzerland), and it establishes the base data for semi-quantitative identification of M. tuberculosis by the Ct value. CTM test were simultaneously conducted on 8,389 specimens submitted to the Samsung Medical Center from January 2015 to December 2015, and the results were analyzed and compared retrospectively investigates the association of the AFB stain with the Ct value of the CTM test, and it establishes the base data for semi-quantitative identification of M. tuberculosis by the Ct value. The Ct values for 135 positive specimens of the CTM were inversely correlated with the AFB stain (rs=−0.545, P＜0.01). When the Ct value of the CTM test and the time to positivity (TTP) of the mycobacteria cultures were verified based on the AFB stain, they were found to have a positive correlation (rs=0.136, P＜0.01). The negative correlation between the CTM test and the AFB stain grade was demonstrated. The clinical significance was verified by applying these criteria to the clinical results. The semi- quantitative criteria of this study can be used to facilitate the rapid isolation of patients with active tuberculosis and infection control in the hospital.

Keywords

• cycle threshold value
• mycobacterium tuberculosis
• real-time pcr
• smear positivity grade