Mucus plugs on CT flag exacerbation and COPD risk even with normal spirometry

Design

Prospective community-based cohort, 3-year follow-up

Population

1,939 Chinese adults with COPD or preserved spirometry

Primary outcome

Exacerbations, lung function decline and incident COPD

Effect

≥3 plugs: exacerbation RR 1.42 (1.11–1.81); incident COPD 18.2% vs 7.6%, RR 1.71

An AJRCCM community cohort in China followed 1,939 adults — 847 with COPD and 1,092 with preserved spirometry — for three years after baseline chest CT; 89% completed follow-up.

In people with preserved spirometry, mucus plugs in 1–2 segments (RR 1.22) or 3 or more segments (RR 1.42) were associated with more exacerbations. Three or more plugs were associated with developing spirometric COPD (18.2% vs 7.6%, RR 1.71) and faster decline in FEV1/FVC. In COPD, including mild and asymptomatic disease, three or more plugs went with more exacerbations.

Mucus plugs are already recognised as a marker of risk in moderate to severe COPD. These data extend that to people whose spirometry is still normal, who are usually reassured.

Many patients have chest CT for other reasons. Mucus plugs reported on a scan are worth acting on with smoking cessation and follow-up spirometry, even when lung function is currently normal.

• Note mucus plugs reported on chest CT, even when spirometry is normal
• Offer smoking cessation support and repeat spirometry to people with plugs in three or more segments
• Ask about cough, sputum and chest infections in people with plugs and preserved spirometry
• Consider mucus plugs alongside symptoms when assessing exacerbation risk in mild COPD

Why it matters

Normal spirometry may be falsely reassuring when the CT shows plugged airways.

Don't overread it

Observational: it does not show that clearing mucus plugs changes outcomes.

The statistics, in plain English

An RR of 1.71 for developing COPD means about 70% higher risk; the interval (1.05 to 2.78) is wide, so the true size could be modest or large.

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