For non-tuberculous mycobacterial (NTM) lung infections, "large gaps still exist in our knowledge" according to the IDSA/ATS guidelines (2007). There are "limitations in systematic data" and recommendations are "based on expert opinion rather than on empirically derived data."
Recognizing these gaps, we reviewed 189 NTM-positive cultures from 113 unique patients from 2013-2014 at our 2-hospital, 1100-bed community-based academic healthcare system. We performed retrospective chart review analyzing demographics, comorbid conditions, specific species identified, treatment, and diagnosis.
Age ranged from 21 to 91 years (mean 64.6 y). There was a slight male predominance (53%) (n=60). The majority were Caucasian (74; 66%), while 25 (22%) were African-American, 7 (6%) were Asian and 5 (4%) were Hispanic. Twelve patients (11%) had >1 NTM species identified; 1 patient had 3 species identified. A majority of patients were symptomatic, mostly with cough (74, 66%), dyspnea (39, 35%), hemoptysis (21, 19%), fever (18, 16%), weight loss (8, 7%). Only 9 (8%) patients were asymptomatic. Common co-morbidities included COPD (40; 35%), bronchiectasis (20; 18%), HIV (11; 10%). Nine (8%9) patients were receiving immunosuppressant medications. Mitral valve prolapse (n=1) and scoliosis/kyphosis (n=5) were uncommon in our population.
Of our 113 patients, 64 (57%) met the current ATS/IDSA guidelines for diagnosis of NTM. Only 30 (27%) patients were initiated on therapy, 5 of whom were coinfected with M. tuberculosis and initiated on anti-tuberculosis therapy. 28 patients were diagnosed with NTM infections via ICD-9 diagnosis codes.
Ongoing studies must be done into identifying patients with NTM infections to help physicians correctly classify at risk patients and test appropriately. This entity is often misdiagnosed, as the patient population is not well known and it takes some time for these respiratory cultures to come back. NTM is often also regarded as a contaminant and patients are not treated. The multidrug therapy is also a barrier to treatment, as patients may not be able to tolerate it or commit to take multiple drugs for many months. As more studies are done, this will help refine the clinical criteria for diagnosis and more patients may be appropriately diagnosed and treated.