The Importance of Mucus in Detecting Lung Infections

In patient education webinars, bronchiectasis expert Dr. James Chalmers often shares his enthusiasm for sputum.

One of his favorite teaching tools is a sputum color chart 💛💚💛—and for good reason.
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Why Mucus Matters

Mucus is part of the body’s defense system, trapping bacteria and harmful particles before they reach the lungs. But mucus also acts as a signal: when infection strikes, it can become thicker and shift toward a darker or greenish color.

This change is caused by the release of myeloperoxidase (MPO), an enzyme from immune cells called neutrophils. MPO is powerful—it produces reactive oxidants such as hypochlorous acid to kill pathogens and helps form neutrophil extracellular traps (NETs) to capture microbes. While essential in fighting infection, excessive MPO activity can damage lung tissue and fuel chronic inflammation.

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Early Action Is Key

Because bronchiectatic lungs are already scarred and vulnerable, treating infections early is critical. Paying attention to mucus changes gives us a valuable head start. If you notice your sputum becoming darker, thicker, or more greenish, it’s important to:

• Notify your doctor right away
  
  
• Provide a sputum sample for testing

Sputum Samples and Standing Orders

It’s a smart idea to keep a few sterile sputum cups at home. Many patients also have a standing order with their local lab. This means you can drop off a sample anytime, and the lab follows your doctor’s pre-filed instructions.
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A typical standing order for bronchiectasis often includes testing for:
🦠 Common respiratory bacteria
🦠 Fungi
🦠 Mycobacteria (via Acid Fast Bacilli / AFB test)—these slow-growing organisms may take up to 8 weeks for results.

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Advocate for Yourself

Facing infection can feel overwhelming and discouraging. But mucus tells us the truth—and by listening, we empower ourselves. Early detection and treatment protect lung health and improve outcomes.
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👉 What do you do when you notice changes in your mucus color or consistency?