Comparative chest computed tomography findings of non-tuberculous mycobacterial lung diseases and pulmonary tuberculosis in patients with acid fast bacilli smear-positive sputum
BMC Pulmonary Medicine
Comparative chest computed tomography findings of non-tuberculous mycobacterial lung diseases and pulmonary tuberculosis in patients with acid fast bacilli smear-positive sputum
Mei-Kang Yuan 1
Cheng-Yu Chang
Ping-Huang Tsai 1 2
Yuan-Ming Lee
Jen-Wu Huang
Shih-Chieh Chang 1 2
0 152 , Xin-Min Road, Yilan City 260 , Taiwan
1 Faculty of Medicine, School of Medicine, National Yang-Ming University , Taipei , Taiwan
2 Department of Internal Medicine, National Yang-Ming University Hospital
Background: Early diagnosis and treatment of nontuberculous mycobacterial lung diseases (NTM-LD) and pulmonary tuberculosis (PTB) are important clinical issues. The present study aimed to compare and identify the chest CT characteristics that help to distinguish NTM lung disease from PTB in patients with acid-fast bacilli (AFB) smear-positive sputum. Methods: From January 2009 to April 2012, we received 467 AFB smear-positive sputum specimens. A total of 95 CT scans obtained from the 159 patients were analyzed, 75 scans were from patients with PTB and 20 scans from NTM-LD. The typical chest CT findings of mycobacterial diseases were analyzed. Results: In patients with PTB, the prevalence of pleural effusion (38.7% vs. 15.0%; P =0.047), nodules < 10 mm in size (76.0% vs. 25.0%; P < 0.001), tree-in-bud pattern (81.3% vs. 55.0%; P =0.021), and cavities (31.1% vs. 5.0%; P =0.018) were significantly higher than patients with NTM. Of the 20 patients with NTM lung diseases, bronchiectasis and cystic changes were significantly higher than patients with PTB (20.0% vs. 4.0%; P = 0.034). In multivariate analysis, CT scan findings of nodules was independently associated with patients with diagnoses of PTB (odds ratio [OR], 0.07; 95% confidence interval [CI], 0.02-0.30). Presence of bronchiectasis and cystic changes in CT scans was strongly associated with patients with NTM-LD (OR, 33.04; 95% CI, 3.01-362.55). Conclusions: The CT distinction between NTM-LD and PTB may help radiologists and physicians to know the most likely diagnoses in AFB-smear positive patients and avoid unnecessary adverse effects and the related costs of anti-TB drugs in endemic areas.
Nontuberculous mycobacterial lung disease; Pulmonary tuberculosis; Acid-fast bacilli smear; Bronchiectasis and cystic changes
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Background
The diagnosis and treatment of pulmonary diseases
caused by mycobacterial infections are very important
clinical issues. Among mycobacterial diseases, pulmonary
tuberculosis (PTB) is the major entity and one of the
worlds leading infectious diseases. In 2012, 8.6 million
people felt ill with TB and 1.3 million died from TB [1].
Isolation of Mycobacterium tuberculosis from respiratory
specimens is recommended for the definite diagnosis of
PTB [2]. Microscopic examination of sputum smears for
acid-fast bacilli (AFB) is widely used and the most efficient
procedure for the initial screening of PTB. The presence
of AFB in the stained sputum (AFB smear-positive)
indicates a preliminary diagnosis of pulmonary mycobacterial
infection. However, positive AFB smear test is not specific
for PTB [3-5]. AFB smear-positive sputum may represent
mycobacterium tuberculosis, but it can also represent
non-tuberculous mycobacteria (NTM) [6]. NTM are
ubiquitous organisms and its radiographic abnormalities
and clinical symptoms changes slowly as compared with
PTB [7]. In endemic areas, it is not uncommon to
administer empirical anti-TB drugs in clinically suspected PTB
patients with AFB smear-positive sputum. The isolation
prevalence of NTM has increased gradually, which raise
the concerns of unnecessary adverse effect and costs of
anti-TB drugs [8,9]. Therefore, additional diagnostic tools
that help differentiate PTB and NTM is relevant in
patients pending culture results. Radiological
manifestations such as computed tomography (CT) features are
useful to aid the diagnosis of PTB and NTM before
definite mycobacterial culture because of its great availability
and short examination time [10]. The aim of this study is
to compare and identify the chest CT characteristics that
help to distinguish NTM lung disease from PTB in
patients with AFB smear-positive sputum.
Methods
Patients
From January 2009 to April 2012, we received 9,267
sputum specimens from 3,958 patients at the laboratory
of National Yang-Ming University Hospital (a 512-bed
regional teaching hospital in Yilan, Taiwan) and the Far
Eastern Memorial Hospital (a 1050-bed tertiary medical
center in Taipei, Taiwan). Of these sputum specimens,
467 from 236 patients were AFB stain-positive. Only 134
of the AFB stain-positive patients had proven pulmonary
TB, and 25 patients proven NTM lung diseases. A total
of 95 CT scans obtained from the 159 patients were
analyzed, 75 scans were from patients with PTB and 20
scans from NTM lung disease. The study was approved
by the Institutional Review Boards of the National
YangMing University Hospital and the Far Eastern Memorial
Hospital. All participant (...truncated)