In a 53‑year‑old female with chronic obstructive pulmonary disease, how should I interpret spirometry showing a forced expiratory volume in one second/forced vital capacity ratio of 85 %, forced expiratory volume in one second 84 % of predicted, forced vital capacity 78 % of predicted, and forced expiratory flow 25‑75 % of predicted 98 %?

Spirometry Interpretation: Normal Pattern, Not COPD

These spirometry results do not show COPD—the FEV1/FVC ratio of 85% is well above the threshold for obstruction, and the pattern suggests either normal lung function with mild restriction or incomplete effort rather than obstructive disease. 1, 2

Primary Pattern Analysis

The FEV1/FVC ratio of 85% is the critical finding here:

• This ratio is above the lower limit of normal for obstruction, which requires values below the 5th percentile (typically <70-75% depending on age) to diagnose airway obstruction 1, 3
• The European Respiratory Society guidelines confirm that a ratio of 85% indicates normal airway caliber relative to lung volume, effectively ruling out COPD 1, 2
• The diagnosis of COPD requires a reduced FEV1/FVC ratio below the 5th percentile—this patient does not meet this fundamental criterion 1

Volume Reduction Pattern

Both FEV1 (84% predicted) and FVC (78% predicted) are mildly reduced but proportionally decreased:

• When FEV1 and FVC are concomitantly decreased with a normal FEV1/FVC ratio, this pattern most frequently reflects incomplete inhalation/exhalation effort rather than true lung disease 1, 2
• The FEF25-75% of 98% is normal, which argues against small airways disease that would be expected in early COPD 1, 4
• This pattern requires total lung capacity (TLC) measurement to distinguish between true restriction, poor effort, or peripheral airway dysfunction 1, 2, 5

Recommended Next Steps

Obtain lung volume measurements (TLC, RV, RV/TLC) by body plethysmography to clarify the diagnosis:

• If TLC is <5th percentile: confirms true restrictive defect (interstitial disease, chest wall disorder, neuromuscular disease) 1, 2, 5
• If TLC is normal with increased RV: suggests peripheral airway dysfunction or air trapping 1, 2
• If TLC and RV are normal: indicates poor effort or technique during spirometry 1, 2, 5

Repeat spirometry with careful coaching may be warranted if poor effort is suspected, as inadequate technique is the most common cause of this pattern 1, 2

Critical Pitfalls to Avoid

• Do not diagnose COPD based on reduced FEV1 alone—the FEV1/FVC ratio is the defining criterion for obstruction, and this patient's ratio is normal 1, 3
• Do not diagnose restriction based on spirometry alone without confirming with TLC measurement, as this leads to frequent misdiagnosis 1, 2, 5
• Avoid using the fixed 70% cutoff for FEV1/FVC in isolation, as it misclassifies patients at extremes of age—this patient's ratio of 85% is clearly above any reasonable threshold 3, 6, 7
• Do not overlook that the normal FEF25-75% (98%) argues strongly against obstructive airways disease, as this measure would typically be reduced disproportionately in early COPD 1, 4

Clinical Context

Given the stated diagnosis of COPD, there are three possibilities:

1. Misdiagnosis: The spirometry does not support COPD—consider alternative diagnoses
2. Treated/improved COPD: If previously obstructed, treatment may have normalized the ratio (though this would be unusual)
3. Technical issues: Poor effort or technique during testing

Review the clinical history, symptoms, smoking status, and prior spirometry results to determine if COPD was ever documented with a reduced FEV1/FVC ratio 1. If this is the first spirometry or if prior tests also showed normal ratios, the COPD diagnosis should be reconsidered.