NTM lung disease: Assessment and determining course of treatment
Click Here to Manage Email Alerts
Nontuberculous mycobacterial (NTM) lung disease is a chronic and debilitating condition, and although considered rare, some studies have estimated that prevalence is increasing about 8% each year in the United States. In 2019, it was estimated that 98,000 to 113,000 patients were diagnosed with the condition, according to unpublished data.
Before seeing an infectious disease specialist or pulmonologist, many patients with NTM lung disease initially present to their primary care physician for evaluation of a chronic cough. Additionally, patients may also have symptoms such as dyspnea, fatigue, weight loss and/or night sweats. However, because many of these symptoms may be associated with other underlying pulmonary diagnoses that a patient is already being treated for — such as bronchiectasis, chronic obstructive pulmonary disease (COPD) or asthma — NTM infection may not be suspected.
If patients are being treated for one of these lung conditions but their symptoms have not improved or are worsening, it is important to consider the possibility of NTM lung disease. Once NTM lung disease is suspected, patients are often referred to an ID specialist for further assessment and to determine the specifics of the disease. If diagnosis is delayed, NTM lung disease may result in long-term damage, and ID specialists play an important role in overall treatment and management.
The evaluation process
Beyond assessing the symptoms listed earlier, it is critical to conduct a thorough evaluation of a patient’s medical history, including childhood, neonatal and fertility history; any previous upper respiratory issues; or history of autoimmune disease. During the initial evaluation, it also is critical to ask patients about their environmental exposures, such as hot tub and indoor pool use or gardening, which may increase the risk for introducing mycobacteria into their airways and subsequently developing NTM lung disease. It also is important to ask about family history, such as a history of cystic fibrosis, bronchiectasis, alpha-1 antitrypsin deficiency or other pulmonary diseases, which may provide clues to underlying causes of structural airway disease or bronchiectasis that make them more vulnerable to infection.
Typically, once an ID specialist is engaged, the diagnosis of NTM lung infection or disease has already been established by the presence of positive sputum cultures. Part of the role of the ID specialist is to evaluate the severity of the infection and ensure the mycobacteriology laboratory identifies the specific species. This may require a phone call to the lab or obtaining new pulmonary specimens from the patient. Sputum samples should be sent to the microbiology lab for routine respiratory, acid-fast bacilli (AFB) and fungal cultures. Patients also should receive a high-resolution CT scan of the chest. It is recommended by the 2007 American Thoracic Society/Infectious Disease Society of America statement on diagnosis to assess clinical, microbiologic and radiographic criteria when evaluating a patient for NTM lung disease.
Species identification and impact on treatment choice
In order to evaluate the aforementioned microbiologic diagnostic criteria, it is essential to work closely with the microbiology laboratory during evaluation of AFB specimens to accurately identify the exact species of NTM bacteria. Ultimately, knowing the specific species causing the patient’s symptoms will help inform the prognosis and the treatment plan. This can be challenging because there are almost 200 different species of NTM identified, not all of which are pathogenic. However, the most common pathogens for lung disease in the U.S. are Mycobacterium avium complex (MAC), Mycobacterium kansasii and Mycobacterium abscessus. More than 80% of mycobacterial lung disease is caused by a MAC species, such as M. avium, Mycobacterium intracellulare and Mycobacterium chimaera.
Susceptibility testing also helps determine the presence or absence of macrolide resistance, which does have prognostic significance in the treatment of these patients. Conducting minimum inhibitory concentration tests is important for defining the appropriate dosing to achieve therapeutic levels, as well antibiotic choice. Working directly with the mycobacteriology lab can ensure best practices are being instituted because ID specialists are typically considered content experts throughout this process.
Once all diagnostic criteria have been evaluated and the patient has been deemed a candidate for treatment, a multidrug antibiotic regimen should be prescribed. This combination of antibiotics is determined based on a patient’s comorbidities, disease severity and progression, NTM species and subspecies, and willingness to initiate therapy. As ID specialists, it will be critical to monitor the patient’s condition to limit the development of resistance over time and assess progress since all patients respond differently to treatment.
Disease management and monitoring
When a patient begins treatment, it is beneficial to review all medications he or she will be taking, including potential side effects, as well as strategies to mitigate these effects. This involves routine follow-up to monitor vital lab results, as well as baseline ophthalmologic and audiologic evaluation. Follow-up typically should be performed every 3 months after treatment initiation.
Clinical response is one of the most important aspects of monitoring progress. Encourage patients to be open about their treatment experience, including improvement, stability or worsening of symptoms and overall sense of well-being. Patients often require follow-up with other specialists, including nutritionists, respiratory therapists and pulmonologists to manage primary lung disease, rheumatologists to manage potential underlying autoimmune disease and behavioral specialists to help patients cope with the depression and anxiety that may often be associated with chronic disease. Collaboration and communication across disciplines is key to monitoring treatment progress.
Additionally, obtaining and testing monthly sputum samples help determine when the patient’s sputum culture converts to negative. Depending on the state of his or her disease, this may take several months. It is important to communicate the expected duration of therapy to the patient and his or her caregiver at treatment initiation to manage expectations. According to guidelines, treatment duration is typically 12 months beyond sputum culture conversion to negative, optimally with 12 months of negative cultures. It will also be important to send the patient for follow-up radiographic imaging 3 to 6 months after initiation of therapy, depending on the clinical situation, to assess for radiographic improvement.
Finally, in addition to antibiotics, lifestyle changes may be recommended to help alleviate symptoms and reduce exposure to NTM. This may include exercise to promote better airway clearance and maintain fitness and stamina, as well as optimal nutrition management for weight maintenance and healing. Overall, partnering with patients and their loved ones on the treatment plan and associated monitoring may promote adherence and better treatment outcomes.
- References:
- Adjemian J, et al. Am J Respir Crit Care Med. 2012;doi:10.1164/rccm.201111-2016OC.
- Adjemian J, et al. Ann Am Thorac Soc. 2014;doi:10.1513/AnnalsATS.201304-085OC.
- Donohue MJ, et al. Environ. Sci Technol. 2015,doi:10.1021/acs.est.5b00496.
- Falkinham JO III. Curr Environ Health Rep. 2016;doi:10.1007/s40572-016-0086-z.
- Griffith DE, et al. Am J Respir Crit Care Med. 2007;doi:10.1164/rccm.200604-571ST.
- Johnson MM, Odell JA. J Thorac Dis. 2014;doi:10.3978/j.issn.2072-1439.2013.12.24.
- Kotilainen H. et al. Eur J Clin Microbiol Infect Dis. 2015;doi:101007/s10096-015-2432-8.
- Park HY, et al Chest. 2016;doi:10.1016/j.chest.2016.06.005.
- Strollo SE, et al. Ann Am Thorac Soc. 2015;doi:10.1513/AnnalsATS.201503-173OC.
- Young JD, et al. J Respir Dis. 2007;28(1):7-18.
- For more information:
- Wendi Drummond, DO, is an ID specialist at Providence Portland Medical Center in Portland, Oregon, and affiliate assistant professor at Oregon Health & Science University-Portland State University School of Public Health.
Disclosure: Drummond reports receiving consulting or grant support from Insmed Inc.
Collapse
Click Here to Manage Email Alerts