What does yellowish green mucus indicate, and how should it be treated, considering potential underlying respiratory conditions?

Yellowish-Green Mucus: Clinical Significance and Management

Yellowish-green mucus does NOT reliably indicate bacterial infection and should NOT be used as the sole criterion for prescribing antibiotics. 1, 2

What Yellowish-Green Mucus Actually Indicates

The yellow-green coloration comes from polymorphonuclear leukocytes (neutrophils) and their enzymes—specifically myeloperoxidase—that accumulate during both viral and bacterial infections, making color alone a poor discriminator between the two. 1, 2

• The presence of purulent sputum reflects inflammatory cells or sloughed mucosal epithelial cells, not necessarily bacteria. 1
• While yellowish or greenish sputum shows statistical correlation with bacterial infection (sensitivity 79%, specificity only 46%), the positive likelihood ratio of 1.46 is too weak to guide treatment decisions. 3
• More than 90% of otherwise healthy patients with acute cough have viral infections, regardless of sputum color. 1

When to Consider Bacterial Infection (and Antibiotics)

For Acute Bronchitis/Cough in Otherwise Healthy Adults:

Do NOT prescribe antibiotics based on sputum color alone. 1, 2

• Antibiotics are not recommended regardless of mucus color, as most cases are viral. 1
• Focus on symptomatic treatment: nasal saline irrigation, analgesics, intranasal corticosteroids, and short-term decongestants. 2

For Acute Rhinosinusitis:

Prescribe antibiotics ONLY when meeting criteria for Acute Bacterial Rhinosinusitis (ABRS): 2

1. Persistent symptoms ≥10 days without improvement (nasal discharge, congestion, facial pain/pressure) 2
2. Severe symptoms for ≥3 consecutive days: fever >39°C (102.2°F) + purulent nasal discharge + facial pain 2
3. "Double sickening": initial improvement followed by worsening with new fever ≥38°C (100.4°F) or substantially worse discharge/cough 2

For COPD Exacerbations:

Consider antibiotics when all three Anthonisen Type I criteria are present: 1

1. Increased dyspnea
2. Increased sputum volume
3. Increased sputum purulence

• May also benefit patients with two of these symptoms (Type II) if purulent sputum is one of them. 1
• Patients requiring mechanical ventilation should receive antibiotics regardless of sputum appearance. 1
• Limit antibiotic duration to 5 days when prescribed. 1

For Suspected Pneumonia:

Assess for pneumonia FIRST by checking: 4

• Tachycardia (≥100 bpm), tachypnea (≥24 breaths/min), fever (≥38°C) 4
• Abnormal chest examination: focal consolidation (rales, egophony, fremitus) 4
• Oxygen saturation <90% 4

If any vital sign abnormalities or focal chest findings are present, obtain chest radiography immediately. 4 If pneumonia is confirmed, prescribe appropriate antibiotics (e.g., levofloxacin monotherapy or ceftriaxone plus azithromycin). 4

Critical Pitfalls to Avoid

• Do NOT diagnose bacterial infection based on purulent mucus color alone—this is the most common error leading to inappropriate antibiotic use. 1, 2
• Do NOT prescribe antibiotics for symptoms lasting <7-10 days without severe features, as this is likely viral. 2
• Do NOT assume fever presence reliably differentiates bacterial from viral disease—temporal patterns and symptom severity matter more. 2
• Inappropriate antibiotic prescribing drives resistance that persists up to 12 months in individuals. 2
• Antibiotics cause significantly more adverse events (RR 1.28) compared to placebo in post-viral rhinosinusitis with no improvement in cure rates. 2

Monitoring and Follow-Up

• Reassess patients at 3-5 days after treatment initiation if antibiotics were prescribed. 5, 4
• For rhinosinusitis, follow up at 2 weeks post-treatment to assess for relapse. 4
• Instruct patients to return if symptoms worsen after initial improvement, new high fever develops, or symptoms persist beyond 28 days. 2