In a 12-year-old girl with spirometry showing forced vital capacity 63% of predicted, forced expiratory volume in one second 82% of predicted, and FEV1/FVC ratio 72%, is asthma likely?

Asthma is Unlikely Based on This Spirometry Pattern

This 12-year-old girl's spirometry results do NOT suggest asthma. The pattern shows a restrictive defect (low FVC at 63% predicted) with a preserved FEV1/FVC ratio of 72%, which is inconsistent with the obstructive airflow limitation that characterizes asthma 1.

Why This Pattern Argues Against Asthma

Spirometry Interpretation

According to the 2021 European Respiratory Society guidelines for diagnosing asthma in children aged 5-16 years, abnormal spirometry suggestive of asthma requires either:

• FEV1/FVC ratio below the lower limit of normal (LLN) or <80%, OR
• FEV1 below LLN or <80% predicted 1

This patient's values:

• FVC: 63% predicted (markedly reduced)
• FEV1: 82% predicted (borderline normal)
• FEV1/FVC: 72% (preserved ratio, though slightly reduced)

The key issue here is that while the FEV1/FVC ratio is mildly reduced at 72%, this occurs in the context of a severely reduced FVC (63%). This pattern suggests a restrictive process, not the obstructive pattern typical of asthma 2.

Critical Distinction: Restrictive vs. Obstructive Pattern

In asthma, you expect:

• Reduced FEV1/FVC ratio (typically <80% or below LLN)
• Normal or near-normal FVC with disproportionately reduced FEV1
• Reversibility with bronchodilator (≥12% and/or ≥200 mL improvement in FEV1) 1

This patient shows:

• Severely reduced FVC (63% predicted) - the primary abnormality
• Relatively preserved FEV1 (82% predicted)
• Mildly reduced FEV1/FVC ratio as a mathematical consequence of low FVC, not true obstruction

Recommended Diagnostic Approach

Immediate Next Steps

1. Perform bronchodilator reversibility (BDR) testing - This is essential to determine if there is any reversible airflow obstruction 1

   • Positive BDR: ≥12% AND/OR ≥200 mL improvement in FEV1 or FVC
   • If BDR is negative with this pattern, asthma becomes even less likely

2. Measure FeNO (fractional exhaled nitric oxide) 1

   • FeNO ≥25 ppb would suggest eosinophilic airway inflammation
   • FeNO <25 ppb makes asthma unlikely

3. Investigate the restrictive pattern - A severely reduced FVC (63% predicted) requires evaluation for:

   • Poor spirometry technique (most common in children)
   • Chest wall abnormalities
   • Neuromuscular conditions
   • Interstitial lung disease
   • Obesity
   • Prior lung injury

Important Caveats

The ERS guidelines emphasize that at least two abnormal objective tests are required to diagnose asthma in children 1. A single abnormal spirometry result, especially one showing a restrictive rather than obstructive pattern, is insufficient for diagnosis.

Normal spirometry does not exclude asthma 1, but this patient doesn't have normal spirometry - she has an abnormal pattern that is inconsistent with typical asthma physiology.

If Strong Clinical Suspicion Persists

If symptoms strongly suggest asthma despite these findings:

• Repeat spirometry when symptomatic 1
• Consider bronchial challenge testing (methacholine or exercise challenge) if BDR and FeNO are negative 1
• Monitor peak expiratory flow rate (PEFR) variability - ≥12% variability supports asthma 1

What NOT to Do

Do not start empiric asthma treatment based on symptoms alone 1. The guidelines explicitly recommend against using symptomatic improvement with inhaled corticosteroids as a diagnostic criterion. Objective testing must confirm the diagnosis.

Bottom Line

This spirometry pattern (low FVC with preserved FEV1/FVC ratio) represents a restrictive defect, not the obstructive pattern characteristic of asthma. Before considering asthma, ensure proper spirometry technique, perform BDR testing and FeNO measurement, and investigate alternative causes for the restrictive pattern. The diagnosis of asthma requires at least two abnormal objective tests demonstrating variable expiratory airflow limitation 1.