A rapid method of diagnosing pulmonary tuberculosis using stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry

A fast method for detection of tuberculostearic acid (TBSA) in sputum samples is described. The samples, obtained from patients with known or suspected pulmonary tuberculosis, were decontaminated and concentrated before being analyzed by stir bar sorptive extraction–thermal desorption–gas chromatography–mass spectrometry (SBSE–TD–GC–MS). Prior to extraction, the mycobacterial lipids were hydrolyzed and then derivatized with ethyl chloroformate to increase the sorption of the compounds by the polydimethylsiloxane (PDMS) stir bar coating. The limit of detection (LOD) is 0.2 ng ml−1. Four sputum samples that were classified by direct microscopy as smear-positive or negative were analyzed by GC–MS. TBSA was detected at concentrations ranging from 0.47 to 2.3 ng ml−1. The method is sufficiently sensitive to detect TBSA directly in clinical samples without the need to culture the organisms.