Strain Identification and Drug Resistance Analysis of Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry in Nontuberculous Mycobacterial Lung Disease

Objective: To evaluate the clinical value of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) in detecting Nontuberculous mycobacteria (NTM).Methods: The clinical data of 172 patients with suspected NTM lung disease were collected from our hospital from January 1, 2018, to December 30, 2021. The results were compared with those of BACTEC MGIT 960 in liquid culture and gene chip. This study also utilised MALDI-TOF MS to detect macrolide (MA) and amikacin (Am) mutations.Results: One hundred thirty-seven cases of NTM pulmonary disease were confirmed by identifying the NTM gene chip in bronchoalveolar lavage fluid and/or MALDI-TOF MS detection. The positive predictive value and negative predictive value were 100% (131/131) and 85.37% (35/41), respectively, and the consistency of the two methods was high (kappa=0.899). For the drug resistance detection of MAs, the consistency rate between MALDI-TOF MS detection and drug sensitivity detection was 97.71% (128/ 131), the sensitivity was 81.25% (13/16) and the specificity was 100% (115/115). The positive and negative predictive values were 100% (13/13) and 93.75% (115/118), respectively. There was no coincidental consistency between the two methods, and the consistency was high (P<0.001, kappa=0.884). For the drug resistance test of Am, the consistency rate between the MALDI-TOF MS test and the drug sensitivity test was 93.13% (122/131), the sensitivity was 93.52% (101/108), the specificity was 90.91% (21/23) and the positive predictive value and negative predictive value were 98.06% (101/103) and 75.00% (21/28), respectively. The two methods had high consistency, and the consistency was not coincidental (P<0.001, kappa=0.781).Conclusion: Utilising MALDI-TOF MS has a good consistency with the drug resistance gene chip method and can be a rapid and effective method to identify strains and drug resistance of NTM. Therefore, it has certain clinical application value in patients with suspected NTM lung disease.

Automated summary

This study evaluated the clinical value of MALDI-TOF MS in detecting NTM by comparing the results with liquid culture and gene chip. The findings showed that MALDI-TOF MS had a high consistency with both methods and could be a rapid and effective method for identifying NTM strains and drug resistance.