From the Journals

Nontuberculous mycobacterial lung disease cases on the rise across U.S.


 

FROM ANNALS OF THE AMERICAN THORACIC SOCIETY

A new study of claims-based data has found that the incidence and prevalence of nontuberculous mycobacterial (NTM) lung disease is increasing in most states.

Dr. George Kubica/CDC

Petri culture plate that had been used to cultivate colonies of the saprotrophic bacteria, Mycobacterium avium, which is commonly found in water and soil.

To assess the NTM lung disease burden on a national level, Kevin L. Winthrop, MD, of Oregon Health & Science University, Portland, and associates analyzed patient data from a U.S. managed care claims database between 2008 and 2015. Their findings were published in the Annals of the American Thoracic Society.

A case of NTM lung disease was defined as a patient with at least two medical claims with the disease’s diagnostic codes – 031.0 and A31.0 – that were at least 30 days apart. Of the 74,984,596 beneficiaries in the database, 9,476 met the case definition for NTM lung disease; 69% (n = 6,530) were women.

From 2008 to 2015, the annual incidence of NTM lung disease increased from 3.13 (95% confidence interval, 2.88-3.40) to 4.73 (95% CI, 4.43-5.05) per 100,000 person-years, with the average rate of yearly change being +5.2% (95% CI, 4.0%-6.4%; P less than .01).The annual prevalence increased from 6.78 (95% CI, 6.45-7.14) to 11.70 (95% CI, 11.26-12.16) per 100,000 persons, with the average rate of yearly change being +7.5% (95% CI, 6.7-8.2%; P less than .01).

The majority of NTM lung disease in the United States is caused by Mycobacterium avium complex (17), although other species such as M. abscessus, M. kansasii, M. xenopi, and others contribute to this disease burden.

“It’s a classic chicken-or-egg scenario,” said Sachin Gupta, MD, a pulmonologist in San Francisco, in regard to the rising numbers. “Increased awareness of NTM lung disease is, in part, why we’re seeing prevalence and incidence go up. And yet the disease itself may also be growing in clusters and pockets, as the data show, in various places across the nation.

“The worrisome aspect here,” he added, “is that future studies will likely show that, as incidence is increasing, mortality is increasing as well. That speaks to the challenges with these bugs: Very hard to diagnose, very hard to treat.”

The authors acknowledged their study’s limitations, including the lack of microbiologic or radiographic confirmation of the NTM infection and the inherent shortcomings of claims data–based studies overall. They did note a previous report, however, that “claims-based case identification has a high positive predictive value of approximately 82% for NTM lung disease.”

The study was funded by Insmed; the Intramural Research Programs of the National Institute of Allergy and Infectious Diseases; and the National Heart, Lung, and Blood Institute. The authors reported no conflicts of interest.

SOURCE: Winthrop KL et al. Ann Am Thorac Soc. 2019 Dec 13. doi: 10.1513/AnnalsATS.201804-236OC.

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