Is an FEV1 (Forced Expiratory Volume in 1 second) to FVC (Forced Vital Capacity) ratio of 68 or 69% significant?

Interpretation of FEV1/FVC Ratio of 68-69%

An FEV1/FVC ratio of 68-69% is clinically significant as it falls below the fixed threshold of 70% used to define airflow obstruction according to GOLD criteria, but interpretation requires consideration of age, symptoms, and other clinical factors to avoid misdiagnosis.

Significance of FEV1/FVC Ratio

• The FEV1/FVC ratio is the primary parameter for detecting airflow obstruction 1
• Two main approaches exist for interpreting this ratio:
  1. Fixed ratio approach: FEV1/FVC < 0.70 (or 70%) indicates obstruction (GOLD criteria)
  2. Lower limit of normal (LLN) approach: FEV1/FVC < 5th percentile of predicted value (ATS/ERS criteria) 1

Interpretation Based on Guidelines

Classification According to ATS/ERS:

• A ratio of 68-69% would be classified as "mild" obstruction if:
  • FEV1/VC is below the 5th percentile of predicted AND
  • FEV1 is ≥70% of predicted value 2

Classification According to GOLD:

• A ratio of 68-69% would be classified as "mild" obstruction if:
  • FEV1/FVC < 0.70 AND
  • FEV1 is >80% of predicted value 2

Age Considerations

• The fixed 70% threshold may lead to overdiagnosis in elderly patients
• In never-smokers aged 70+ years, FEV1/FVC ratios as low as 65% may be considered normal 3
• In patients over 70 years, using the LLN approach is more appropriate to avoid false positive diagnoses 3

Clinical Relevance and Diagnostic Value

• A ratio of 68-69% alone has limited diagnostic value without considering:

  1. Age of the patient
  2. FEV1 percent predicted (severity assessment)
  3. Clinical symptoms
  4. Risk factors (smoking history)

• The combination of FEV1/FVC < 70% AND FEV1 < 80% predicted has 70% accuracy in diagnosing COPD (100% sensitivity but only 38% specificity) 4

Potential Pitfalls

• Overdiagnosis risk: Using fixed ratio alone may lead to COPD overdiagnosis, particularly in elderly patients 5
• Underdiagnosis risk: Some patients with normal FEV1/FVC but abnormal FEV1/SVC (slow vital capacity) may have early obstructive disease 6
• Misclassification: Different grading systems (ATS/ERS vs. GLI) may classify the same patient differently 7

Recommendations for Clinical Practice

1. Consider both criteria: Evaluate both FEV1/FVC ratio AND FEV1 percent predicted
2. Use age-appropriate thresholds: Consider LLN rather than fixed ratio in elderly patients
3. Assess bronchodilator response: Post-bronchodilator values should be used for COPD diagnosis 1
4. Evaluate symptoms: Correlate spirometric findings with clinical presentation
5. Consider alternative measurements: FEV1/SVC may detect early obstruction missed by FEV1/FVC 1, 6

Bottom Line

A FEV1/FVC ratio of 68-69% is below the conventional 70% threshold and warrants further clinical evaluation, but should not be interpreted in isolation. The significance depends on the patient's age, symptoms, and other lung function parameters, particularly FEV1 percent predicted, which determines the severity of any obstruction present.