Analysis of time for diagnosis of nontuberculous mycobacterial lung disease and its associated factors in a tuberculosis-designated hospital in Shanghai

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Objective: To investigate the pathogenic characteristics, bacteriological diagnosis time and its associated factors among patients with nontuberculous mycobacterial (NTM) lung disease in a large tuberculosis-designated hospital in Shanghai from 2020 to 2021, in order to improve diagnosis efficiency and formulate precision treatment. Methods: On the basis of the Tuberculosis Database in Shanghai Pulmonary Hospital, NTM patients diagnosed by the Department of Tuberculosis between January 2020 and December 2021 were screened. Demographic, clinical and bacterial information were retrospectively collected. Chi-square test, paired-sample nonparametric test and logistic regression model were used to analyze the factors associated with the diagnosis time of NTM lung disease. Results: A total of 294 patients with bacteriologically confirmed NTM lung disease were included in this study, 147 males and 147 females with a median age of 61(46, 69) years. Of them, 227 (77.2%) patients had comorbidity of bronchiectasis. Species identification results showed that Mycobacterium Avium-Intracellulare Complex was the main pathogen of NTM lung disease (56.1%), followed by Mycobacterium kansasii (19.0%) and Mycobacterium abscessus (15.3%). Species such as Mycobacterium xenopi and Mycobacterium malmoense were rarely identified, accounting for a total proportion of only 3.1%. Positive culture rates for sputum, bronchoalveolar lavage fluid and puncture fluid were 87.4%, 80.3% and 61.5%, respectively. Paired-sample analysis showed that the positive rate of sputum culture was significantly higher than that of smear microscopy (87.1% vs. 48.4%, P<0.01), while no statistical difference was observed between sputum and bronchoalveolar lavage fluid on positive culture rate (78.7% vs. 77.3%, P>0.05). Patients with cough or expectoration were observed with 4.04-fold (95%CI 1.80-9.05) or 2.95-fold (95%CI 1.34-6.52) higher probability of positive sputum culture, compared to those without. Regarding bronchoalveolar lavage fluid, female or patients with bronchiectasis had a 2.82-fold (95%CI 1.16-6.88) or 2.38-fold (95%CI 1.01-5.63) higher probability to achieve a positive culture. The median time to diagnosis of NTM lung disease was 32 (interquartile range: 26-42) days. The results of multivariable analysis showed that patients with symptom of expectoration (aOR=0.48, 95%CI 0.29-0.80) needed a shorter diagnosis time in comparison with patients without expectoration. With Mycobacterium Avium-Intracellulare Complex as a reference, lung disease caused by Mycobacterium abscessus needed shorter diagnosis time (aOR=0.43, 95%CI 0.21-0.88), whereas those caused by rare NTM species were observed to require a longer diagnosis time (aOR=8.31, 95%CI 1.01-68.6). Conclusion: The main pathogen causing NTM lung disease in Shanghai was Mycobacterium Avium-Intracellulare Complex. Sex, clinical symptoms and bronchiectasis had an impact on the positive rate of mycobacterial culture. The majority of patients in study hospital were timely diagnosed. Clinical symptoms and NTM species were associated with the bacteriological diagnosis time of NTM lung disease.