Sputum proteomic analysis for distinguishing between pulmonary tuberculosis and non-tuberculosis using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS): preliminary results

Objectives The aim was to evaluate the feasibility and diagnostic contribution of protein profiling using matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) applied to sputum to diagnose pulmonary tuberculosis. Methods Sputum samples collected from patients suspected of having pulmonary tuberculosis were analysed using MALDI-TOF MS. Using the differentially expressed protein peaks, we compared three groups of patients, including those with confirmed pulmonary tuberculosis (PTB), those without tuberculosis but with a lower respiratory tract infection (non-TB LRTI) and those without tuberculosis and without an LRTI (non-TB controls). Results A total of 102 patients included 35 PTB, 36 non-TB LRTI and 31 non-TB controls. The model differentiated between the PTB patients and the non-TB controls using the 25 most differentially expressed protein peaks, with a sensitivity of 97%, 95% CI 85-100%, and a specificity of 77%, 95% CI 59-90%. The model distinguished the PTB patients from the non-TB LRTI patients using the ten most differentially expressed protein peaks, with a sensitivity of 80%, 95% CI 63-92%, and a specificity of 89%, 95% CI 74-97%. We observed that the negative predictive value of MALDI-TOF MS sputum analysis was higher (96%, 95% CI 80-100%) than that of direct sputum microscopic examination and sputum culture (78%, 95% CI 62-89%) for non-TB controls. When MALDI-TOF MS sputum analysis and direct microscopic examination were combined, the negative predictive value reached 94%, 95% CI 80-99%, for non-TB LRTI patients. Discussion These results suggest that MALDI-TOF MS sputum analysis coupled with microscopic examination could be used as a screening tool for diagnosing pulmonary TB.