What laboratory tests should be ordered for the workup of COPD, including screening for common comorbidities and disease severity?

Blood Test Workup for COPD

For COPD workup, obtain a complete blood count (CBC), alpha-1 antitrypsin level in patients under 45 or with family history, and consider screening labs for common comorbidities including fasting glucose, lipid panel, and inflammatory markers (CRP), as comorbidities account for the majority of mortality in COPD patients.

Essential Laboratory Tests

Core COPD-Specific Testing

• Complete Blood Count (CBC): Screen for anemia and polycythemia

  • Anemia is present in 4-70% of COPD patients and independently predicts hospitalization and mortality 1
  • Polycythemia may indicate chronic hypoxemia

• Alpha-1 Antitrypsin (AAT) Level: Mandatory in specific populations 2

  • Test all patients with COPD onset before age 45
  • Test patients with strong family history of COPD
  • Test patients with predominantly basilar emphysema
  • AAT deficiency is a validated COPD phenotype requiring specific management

Comorbidity Screening Panel

The evidence is clear that 26% of COPD deaths are cardiovascular, 21% are cancer-related, and only 35% are directly attributable to COPD 3. This makes comorbidity screening essential:

Cardiovascular/Metabolic Screen:

• Fasting glucose or HbA1c (diabetes prevalence is high even after controlling for smoking)
• Lipid panel (dyslipidemia affects 55% of COPD patients) 4
• Basic metabolic panel (assess renal function before starting ACE inhibitors/ARBs)

Inflammatory Markers:

• C-reactive protein (CRP): Elevated in moderate-severe COPD, reflects systemic inflammation 5, 6, 7
• Consider fibrinogen as additional inflammatory marker 5

Blood Eosinophil Count:

• Prognostic value for exacerbation risk 8
• Predicts response to inhaled corticosteroids
• Higher counts may predict increased exacerbation rates

Additional Testing Based on Clinical Presentation

If weight loss or cachexia present:

• Albumin, prealbumin
• Thyroid function tests (TSH, free T4) - thyroid dysfunction affects 6% 4

If recurrent infections or immunodeficiency suspected:

• Serum immunoglobulins (IgG, IgA, IgM) 9
• Specific pneumococcal antibody levels if immunoglobulins low 9

If allergic features present:

• Total IgE and Aspergillus-specific IgE (screen for ABPA) 9

Common Pitfalls to Avoid

1. Don't skip AAT testing in young patients - This is a validated, treatable phenotype that requires specific augmentation therapy

2. Don't ignore anemia - Even mild anemia substantially decreases aerobic capacity and increases mortality risk 1

3. Don't overlook cardiovascular screening - Ischemic heart disease contributes to worse health status, longer exacerbations, and decreased survival 3, 2, 3

4. Don't rely solely on spirometry - COPD is a systemic disease requiring assessment beyond lung function 7

Monitoring Labs

For stable patients on treatment:

• Repeat CBC if on chronic corticosteroids (monitor for polycythemia, leukocytosis)
• Monitor renal function if on ACE inhibitors/ARBs (creatinine up to 250 μmol/L acceptable with specialist supervision) 1
• Potassium monitoring if on aldosterone antagonists (high hyperkalaemia risk) 1

For deteriorating patients:

• Arterial blood gas if respiratory failure suspected
• Troponin if acute cardiovascular event suspected (COPD exacerbations increase cardiovascular event risk) 3
• Repeat inflammatory markers to assess disease activity 6

The structured approach to laboratory testing in COPD should prioritize identifying treatable comorbidities that account for the majority of morbidity and mortality, rather than focusing exclusively on pulmonary parameters 3, 7.