In a 70-year-old woman diagnosed with asthma in her 50s who is stable on Symbicort (budesonide/formoterol) once daily and now shows normal spirometry with no bronchodilator reversibility, could the original asthma diagnosis have been incorrect or has the disease truly resolved?

Can Asthma Resolve or Was the Original Diagnosis Wrong?

Both scenarios are possible in your patient: the original asthma diagnosis may have been incorrect (misdiagnosis is common without objective testing), or she may represent one of the rare cases where asthma has entered prolonged remission, though true resolution in adult-onset asthma is uncommon. 1, 2

Understanding the Current Situation

Your patient's normal spirometry with no bronchodilator reversibility creates diagnostic uncertainty, but this finding alone does not definitively exclude asthma:

• Normal spirometry is common in well-controlled asthma between symptomatic episodes, as asthma is inherently variable 2, 3
• A single normal spirometry has low sensitivity (12-52%) for asthma diagnosis, meaning it frequently misses the disease even when present 2
• Lack of bronchodilator response does not rule out asthma, particularly in patients on controller therapy like Symbicort 2, 4

Was the Original Diagnosis Wrong?

The high probability of initial misdiagnosis must be seriously considered:

• Asthma misdiagnosis rates are alarmingly high when diagnosis relies on clinical history alone without objective testing 1
• Up to 45% of patients with reported asthma are overdiagnosed when subsequently evaluated with objective measures 1
• Many patients labeled as asthmatic never underwent spirometry or bronchodilator testing at the time of initial diagnosis 1
• Empiric treatment trials where symptom improvement alone confirms diagnosis lead to misdiagnosis and should never be used 5

Critical question: Did she ever have documented airflow obstruction with reversibility at diagnosis in her 50s? If not, the original diagnosis was likely presumptive. 2, 5

Could Asthma Have Resolved?

True asthma resolution in adult-onset disease is uncommon but possible:

• Adult-onset asthma (diagnosed in the 50s) typically does not spontaneously resolve and often shows more rapid lung function decline compared to childhood-onset asthma 1
• However, prolonged remission can occur, particularly with excellent disease control on inhaled corticosteroids 6, 7
• Symbicort (budesonide/formoterol) is highly effective and may have achieved such excellent control that airway inflammation and hyperresponsiveness have normalized 6, 7

Next Steps to Clarify the Diagnosis

You must perform additional objective testing before concluding she never had asthma or that it has resolved: 2, 5

Immediate Testing (While Still on Symbicort)

• Measure FeNO (Fractional Exhaled Nitric Oxide): A value ≥25 ppb supports ongoing asthma even with normal spirometry 2, 5
• Peak flow variability monitoring: Have her record twice-daily peak flows for 2 weeks; variability >10% suggests asthma 2, 8

Consider Bronchial Challenge Testing

• Methacholine challenge is indicated when asthma cannot be confirmed with other tests; PC₂₀ <8 mg/mL is diagnostic of airway hyperresponsiveness consistent with asthma 2, 8
• This test has high negative predictive value—if negative, asthma is very unlikely 1

Supervised Medication Reduction Trial

If all additional testing is negative, consider a carefully monitored step-down trial: 8

• Reduce Symbicort dose gradually while monitoring symptoms and serial spirometry every 4-6 weeks 8
• Provide written asthma action plan with clear instructions to restart full-dose therapy if symptoms recur
• Schedule close follow-up to detect early loss of control 1

Common Diagnostic Pitfalls to Avoid

• Do not assume normal spirometry rules out asthma—serial measurements may be needed to capture variable obstruction 2, 4
• Do not stop Symbicort abruptly without a monitoring plan, as this risks severe exacerbation if she truly has asthma 8
• Do not rely on symptom stability alone as evidence against asthma—this may simply reflect excellent treatment response 1, 5
• Fixed FEV₁/FVC ratio cutoffs may be misleading in a 70-year-old; use lower limit of normal when possible 2

Most Likely Scenario

Given the high rates of asthma misdiagnosis when objective testing is not performed initially, and the fact that adult-onset asthma rarely resolves spontaneously, the most probable explanation is that she never had asthma. 1 However, you cannot make this determination with certainty based solely on one normal spirometry while she remains on effective controller therapy. 2, 4

Proceed with additional objective testing (FeNO, peak flow variability, and potentially methacholine challenge) before making any treatment changes. 2, 5, 8