Interpretation of FEV1/FVC 74.6% and FEF25-75 2.89 L/s
Your spirometry shows a borderline-to-normal FEV1/FVC ratio of 74.6% that does not meet criteria for airflow obstruction, but the reduced FEF25-75 suggests possible early small airway disease that may not yet be clinically significant.
Understanding Your FEV1/FVC Ratio
The FEV1/FVC ratio of 74.6% falls above the diagnostic threshold for obstruction, which is defined as <70% by fixed-ratio criteria or below the 5th percentile using age-adjusted reference values 1, 2.
This ratio is technically normal for most adults, as healthy adults should maintain an FEV1/FVC >70-80% 1.
However, age matters significantly in interpretation: If you are elderly (>70 years), this ratio is clearly normal, as the lower limit can drop to 65% in this age group 3. If you are young (<40 years), a ratio of 74.6% may actually represent mild obstruction that the fixed 70% cutoff misses 4, 5.
The fixed 70% threshold misidentifies nearly half of abnormal younger adults as normal and misidentifies approximately one-fifth of normal older adults as abnormal 5.
Understanding Your FEF25-75 Value
The FEF25-75 of 2.89 L/s reflects mid-expiratory flow and is thought to be sensitive for detecting early small airway disease 1.
A reduced FEF25-75 with preserved FEV1/FVC suggests possible early small airway involvement, manifesting as slowing in the terminal portion of the spirogram 1.
However, abnormalities in mid-range flow measurements are not specific for small airway disease in individual patients 1.
In cystic fibrosis populations, FEF25-75 detected obstruction in 31% of cases with normal FEV1, though FEV1/FVC ratio was more sensitive at 72% 6.
Clinical Significance and Next Steps
Without knowing your absolute FEV1 value, FVC value, symptoms, smoking history, and age, definitive classification is impossible, but here is the algorithmic approach:
If You Are Symptomatic (dyspnea, cough, wheezing):
Post-bronchodilator spirometry is mandatory using 400 mcg salbutamol, with reassessment 15 minutes later 2, 7.
A positive bronchodilator response (≥12% AND ≥200 mL improvement in FEV1 and/or FVC) suggests reversible airway disease like asthma 1, 7.
Consider measuring fractional exhaled nitric oxide (FeNO) to assess for eosinophilic airway inflammation if asthma is suspected 1.
If symptoms persist despite normal spirometry, consider bronchial provocation testing through referral to a pulmonologist 1.
If You Are Asymptomatic:
No routine pharmacotherapy is recommended for asymptomatic patients with borderline spirometry 2.
Serial spirometry should be performed to monitor for progression, as changes >200 mL in FEV1 are clinically significant 2.
Critical Age-Based Interpretation:
If you are <40 years old: Your ratio of 74.6% may represent true mild obstruction that requires age-adjusted reference values (5th percentile method) for accurate diagnosis 4, 5.
If you are >70 years old: Your ratio of 74.6% is definitively normal, and ratios down to 65% should be considered normal in this age group 3.
Common Pitfalls to Avoid
Do not diagnose obstruction based on FEF25-75 alone, as it has high variability and poor specificity 1.
Do not ignore the clinical context: Spirometry must be interpreted alongside symptoms, smoking history, occupational exposures, and physical examination findings 1.
Do not use pre-bronchodilator values to diagnose COPD, as post-bronchodilator testing is mandatory 2, 7.
Do not assume a "normal" FEV1/FVC excludes all airway disease, as 75% of tests with normal FEV1 showed other abnormalities in one study 6.