Only about a quarter of people whose sputum grows Mycobacterium avium complex (MAC) have progressive lung disease. The rest are colonized, and separating the two rests on nonspecific cough and CT patterns that blur into the bronchiectasis these patients already carry. A two-hospital Taiwanese study took that problem to blood transcriptomics, sequencing RNA from peripheral blood mononuclear cells (PBMCs) in 120 culture-positive patients. Key Takeaways Blood transcriptomics sep