What is the diagnosis and treatment for a patient with an FEV1 of 95, FVC of 92, FEV1/FVC ratio of 81, and PEF of 53, indicating possible obstructive lung disease?

Spirometry Interpretation: Isolated Low Peak Expiratory Flow

This spirometry shows normal lung volumes (FEV1 95%, FVC 92%) with a preserved FEV1/FVC ratio of 81%, but a markedly reduced peak expiratory flow (PEF 53%), which does not represent obstructive lung disease by standard criteria and most likely reflects poor effort, inadequate technique, or early small airway dysfunction that requires further evaluation.

Systematic Interpretation Approach

Step 1: Assess for Obstruction

• The FEV1/FVC ratio of 81% is above the 5th percentile threshold used to define obstruction, ruling out classic obstructive lung disease 1
• Obstruction requires FEV1/VC below the 5th percentile of predicted values, which is not present here 1, 2
• Both FEV1 (95%) and FVC (92%) are within normal range, further arguing against obstruction 1

Step 2: Assess for Restriction

• FVC of 92% is above the lower limit of normal (5th percentile), ruling out restrictive disease 1
• A restrictive defect requires TLC below the 5th percentile, which cannot be diagnosed from spirometry alone 1
• The normal FEV1/FVC ratio with normal volumes excludes restriction 2

Step 3: Interpret the Isolated Low PEF

The isolated reduction in PEF (53%) with otherwise normal spirometry is most commonly explained by:

• Poor effort or submaximal inspiratory/expiratory maneuvers, which is the most frequent cause of discordant spirometry results 1
• The pattern of concomitantly decreased FEV1 and FVC with normal ratio most commonly reflects failure to inhale or exhale completely 1
• However, your FEV1 and FVC are normal, making isolated PEF reduction even more suggestive of technical issues

Alternative explanations if effort is adequate:

• Early peripheral airway obstruction with patchy collapse of small airways that may not yet affect FEV1/FVC ratio 1
• Upper airway or large central airway narrowing, which can disproportionately affect PEF while preserving FEV1/FVC 1

Recommended Next Steps

Immediate Actions

• Repeat spirometry with careful coaching on technique, ensuring maximal inspiration followed by forceful, rapid exhalation 1
• Review the flow-volume loop shape: look for a "scooped out" or concave expiratory curve that would suggest early obstruction 2
• If the pattern persists with good effort, the flow-volume curve should show whether flows are reduced throughout the volume range 1, 2

If Pattern Persists with Good Effort

• Perform post-bronchodilator spirometry to assess for reversible airflow obstruction 1, 3
  • A positive response is ≥12% and 200 mL improvement in FEV1 or FVC in adults 4, 5
  • Most patients show onset of improvement within 5 minutes, with maximum effect at 1 hour 3
• Measure lung volumes by body plethysmography to assess for hyperinflation (increased RV, TLC, or RV/TLC ratio) that might indicate early obstructive disease 1
• Consider measuring slow vital capacity (SVC) if there is clinical suspicion of peripheral airway disease, as FEV1/SVC may be more sensitive than FEV1/FVC for detecting mild obstruction 1

Clinical Context Matters

• Obtain history of respiratory symptoms (wheezing, dyspnea, cough), smoking exposure, occupational exposures 1
• If symptomatic with strong clinical suspicion of airway disease despite normal FEV1/FVC, pursue additional testing rather than dismissing the findings 1
• Consider bronchoprovocation testing if asthma is suspected and spirometry remains normal 4, 5

Common Pitfalls to Avoid

• Do not diagnose obstruction based on isolated low PEF when FEV1/FVC ratio is normal 1
• Do not assume restriction without measuring TLC, as reduced VC alone does not prove restrictive disease 1, 2
• Do not overlook poor effort as the most common cause of discordant spirometry patterns 1, 2
• Do not use a fixed FEV1/FVC cutoff of 0.70 to define obstruction, as this overestimates disease in older patients; use the 5th percentile instead 1