Prospective outcomes of adults with speciated Mycobacterium avium complex lung disease, 2021-2026

Mycobacterium avium complex lung disease (MAC-LD) is clinically heterogeneous and carries diverse outcomes.

To describe predictors of clinical progression of MAC-LD in a state-wide cohort.

We enrolled adults with MAC-LD from across Virginia, USA starting in 2021. Every 6 months we performed respiratory quality of life questionnaire, scored CT scans, and recorded respiratory mycobacterial cultures including MAC speciation. Outcomes were classified using NTM-NET consensus definitions, factors predicting clinical progression analyzed by Poisson regression, and hierarchical clustering on principal components derived from Factorial Analysis of Mixed Data.

Of 105 participants the median follow-up was 917 days. Mean age was 69.8 years, 79 (75%) were women, and 70 (67%) had nodular bronchiectasis. M. intracellulare was the most common species, present in 48 (46%) participants at enrollment, followed by M. avium (29, 28%), and M. intracellulare subspecies chimaera (11, 10%). Only 2 (9%) of 22 evaluable participants met the NTM-NET definition of cure. In all participants after multivariable adjustment, older baseline age (incidence rate ratio 1.03 [1, 1.06], p = 0.04) and fibrocavitary CT scan pattern (2.57 [1.33, 4.96], p = 0.005), were associated with unfavorable 12-month clinical progression. Species type and species persistence contributed to characteristics of three distinct phenotypes of MAC-LD of varying severity and clinical progression.

The majority of participants were not assessable for MAC-LD treatment outcomes using strict NTM-NET definitions. Species informed phenotypes of MAC lung disease are prognostically useful and can inform routine management and trial design.