Steroids May Increase Risk for Non-TB Mycobacteriosis

Chronic obstructive pulmonary disease (COPD) and other chronic respiratory diseases are strongly linked to risk for nontuberculous mycobacteriosis (NTM), particularly in patients treated with inhaled corticosteroids (ICS), according to results from a population-based case-control study.

Claire Andréjak, MD, from the Department of Respiratory Diseases, Teaching Hospital Amiens in France, and colleagues published the study results online July 10, 2012, and in print February 11, 2013, in a special themed issue of Thorax coinciding with World TB Day.

"The global incidence of [NTM] pulmonary disease averages one case per 100 000 person-years, is probably underestimated, and is increasing," the authors write. "Prognosis is poor: overall 3-year cumulative death rate is 34% and the death rate for certain strains is even higher (69% for Mycobacteria xenopi). However, few data are available on risk factors for NTM."

The investigators matched 10 population controls to each adult case of microbiologically confirmed NTM pulmonary disease in Denmark between 1997 and 2008. Using conditional logistic regression, they calculated adjusted odds ratios (ORs) for NTM pulmonary disease on the basis of history of chronic respiratory disease.

Risk for NTM pulmonary disease was increased 16.5-fold (95% confidence interval [CI], 12.2-fold to 22.2-fold) in patients with any type of chronic respiratory disease, after adjusting for level of comorbidity and alcoholism-related conditions. The highest adjusted ORs for NTM disease were for history of bronchiectasis (187.5; 95% CI, 24.8 - 1417.4) and tuberculosis (178.3; 95% CI, 55.4 - 574.3). ORs were also increased for asthma (7.8; 95% CI, 5.2 - 11.6) and pneumoconiosis (9.8; 95% CI, 2.03 - 52.8).

For patients with COPD currently treated with ICS, the OR was 29.1 (95% CI, 13.3 - 63.8) compared with 7.6 (95% CI, 3.4 - 16.8) for patients with COPD never treated with ICS. As ICS dose increased, so did the ORs (28.1 for low-dose intake less than 800 μg/day and 47.5 for 800 μg/day or more). OR for fluticasone was higher than for budesonide. COPD analyses were adjusted for "level of comorbidity, alcoholism-related conditions, use of oral corticosteroids and other immunosuppressive therapy the year before non-tuberculous mycobacterial disease diagnosis, marital status and urbanisation of place of residence."

"This population-based case–control study provides strong evidence that the risk of NTM pulmonary disease is substantially increased in adults with asthma, COPD, bronchiectasis and previous tuberculosis," the study authors write.

"Among patients with COPD, the risk of NTM pulmonary disease is clearly associated with use, dose and type of inhaled corticosteroid."

Limitations of this study include the possibly limited generalizability and overestimation of NTM pulmonary disease risk and the inability to determine the role of smoking and other lifestyle factors.

"Clinicians should be aware of this association and use all available diagnostic tools to confirm or rule out definitive NTM pulmonary disease, including at least three sputum samples and a chest x-ray or chest [computed tomography scan] in patients with COPD and other chronic respiratory diseases," the study authors conclude.

The Karen Elise Jensen Foundation, Denmark, supported this study. The study authors have disclosed no relevant financial relationships.

Thorax. 2013;68:256-262. Abstract