Mycobacterium abscessus pulmonary disease (MAPD) is a complex lung disease with increasing prevalence. Little is known on its influence on long term lung function. This study investigated the impact of MAPD on longitudinal lung function over a 7 year period in Singapore.

Objective: 
To investigate the impact of MAPD on lung function in bronchiectasis patients in a tertiary referral centre from 2016 to 2022.

Method:
Demographic and clinical profiles of the study cohort were analysed prospectively. MAPD was diagnosed based on American Thoracic Society and Infectious Disease Society of America (ATS/IDSA) criteria. Patients with idiopathic bronchiectasis were categorised as the control group.

Results:
23 patients fulfilled criteria for MAPD. 68 patients fulfilled criteria for the control group. The median age of MAPD and control was 65 and 73 years respectively (p=0.001). MAPD patients had lower BMI than control (18.3 vs. 21.6, p=0.0004).
 
The median rate of FEV₁ decline (ml/year) was greater in MAPD patients than control (77ml/year vs. 22ml/year, p=0.041). The median rate of decline in predicted FEV₁ (%/year) was similar in both groups (2.9% vs 0%, p=0.06). The annual rate of decline in FVC was similar in both groups. MAPD patients had an average daily sputum volume reduction of 10ml annually compared to an increase of about 3ml for the control group. The modified MRC dyspnoea score annually was similar in both groups.

Conclusion: 

Patients with MAPD had a significant rate of decline of FEV₁ compared to idiopathic bronchiectasis. MAPD patients had lower BMI and were younger than patients with idiopathic bronchiectasis. Future study on interventions that change the course of disease is crucial.