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by Zeena Nackerdien PhD, CME Writer, MedPage Today Recent estimates point to a rise in NTM lung disease in the U.S., particularly among those older than 50 or those with chronic underlying lung diseases, such as non-cystic fibrosis bronchiectasis, cystic fibrosis, and emphysema. According to a 1997-2007 estimate of the Medicare population (≥65 years old), NTM lung disease increased at an annual rate of 8.2%. In Annals of the American Thoracic Society, Kevin Winthrop, MD, of Oregon Health and Science University in Portland, and colleagues provided a more comprehensive and contemporary estimate (2008-2015) of the annual incidence and prevalence of NTM lung disease in the U.S. They found that NTM lung disease continued to increase, especially among seniors (≥65 years old) and women. "Our findings add to other recent studies from North America and other regions of the world that show NTM disease is increasing," said Winthrop in a press release. Researchers used Optum Clinformatics Data Mart, a de-identified claims database from a national insurance provider. Individuals with NTM lung disease were defined as those who had at least two medical claims with International Classification of Diseases (ICD) clinical modification codes of ICD-9-CM 031.0 or ICD-10-CM A31.0 dated at least 30 days apart. Over the course of the study period, the annual incidence of NTM lung disease increased from 3.13 (95% CI 2.88-3.40) to 4.73 (95% CI 4.43-5.05) per 100,000 person-years and the annual prevalence rose from 6.78 (95% CI 6.45-7.14) to 11.70 (95% CI 11.26-12.16) per 100,000 persons, meaning that the average annual changes in incidence and prevalence were +5.2% and +7.5%, respectively. Looking specifically at women, the annual NTM lung disease incidence increased from 4.16 (95% CI 3.76-4.60) to 6.69 (95% CI 6.19-7.22) per 100,000 person-years. Correspondingly, the annual prevalence increased from 9.63 (95% CI 9.08-10.22) to 16.78 (95% CI 16.04-17.55) per 100,000 persons. Among seniors, the annual incidence increased from 12.70 (95% CI 11.46-14.07) to 18.37 (95% CI 16.98-19.87) per 100,000 person-years and the annual prevalence increased from 30.27 (95% CI 28.41-32.24) to 47.48 (95% CI 45.37-49.67) per 100,000 persons. Looking at geographic variations, researchers found that the incidence and prevalence of NTM lung disease increased in most U.S. states (incidence increased by at least 10% in 29 states, and prevalence increased by at least 10% in 39 states) and overall at the national level. According to the 2007 American Thoracic Society/Infectious Diseases Society of America guidelines, clinical, radiographic, and microbiological criteria have to be included in the diagnosis of NTM lung disease. Hence, the use of only real-world ICD coding had inherent drawbacks. In addition, intrinsic deficiencies in the diagnostic coding system may, to some degree, have impaired the accurate diagnosis and recording of cases. Because the researchers lacked access to socioeconomic data, they could also not ascertain how these factors might have impacted NTM lung disease incidence and prevalence. Source Reference: Annals of the American Thoracic Society 2019; DOI: 10.1513/AnnalsATS.201804-236OC Study Highlights and Explanation of Findings: Over the course of the study period (2008-2015), the incidence and prevalence of NTM lung disease appeared to be increasing in the U.S., especially among women and people older than 65. "There are likely multiple reasons for these increases," Winthrop said in the press release. "The number of people at risk is increasing because the population is aging and more people are living with chronic lung diseases. Increasing environmental exposure is also likely a factor, as is greater awareness of NTM disease among physicians." He added that the high rates of NTM lung disease among women may be explained by the fact that they live longer and may be more likely to seek medical care. There may also be as yet unidentified biologic and genetic factors that contribute to greater incidence and prevalence among women. Researchers pointed out that the 7.5% increase in prevalence observed from 2008 to 2015 in the current study was comparable to a previously reported 8.2% increase noted in a 1997-2007 analysis of Medicare Part B claims. They ascribed the slight differences between the studies to the difference in identification criteria for NTM lung disease. In addition, age was likely a driver of the higher prevalence of NTM lung disease among Medicare Advantage beneficiaries relative to commercially insured beneficiaries in the current study. Using four healthcare delivery systems combined, another U.S.-based study showed that the average annual age-adjusted period prevalence for 2004 to 2006 was 5.5 cases per 100,000 persons. This result was in keeping with the overall NTM lung disease prevalence rate for 2008 reported in the present study (6.78 cases per 100,000 persons). Previously, an Oregon-based study showed a relatively small increase of 2.2% (P=0.21) in the annual incidence of NTM lung disease from 2007 to 2012 (from 4.8/100,000 person-years to 5.6/100,000 person-years). By comparison, the present study showed an incidence of NTM lung disease in Oregon of 3.01-4.00 per 100,000 person-years in 2008 and 4.51-6.00 per 100,000 person-years in 2015. Study strengths, according to the authors, included the use of a large nationwide, geographically diverse claims database and the use of two diagnostic codes at least 30 days apart to define disease. Reviewed by: Henry A. Solomon, MD, FACP, FACC Clinical Associate Professor, Weill Cornell Medical College