This real-world case study reveals why objective testing is essential for every patient—and how it can prevent misdiagnosis and unnecessary treatment.

Why Objective Testing Matters

Objective testing is a cornerstone of both asthma diagnosis and management. Yet, it remains underutilized, leading to overdiagnosis or underdiagnosis of asthma. When patients are misdiagnosed, they may receive medications they don’t need, face financial burdens, and experience unwanted side effects. More importantly, misdiagnosis delays the identification and management of the actual disease.

Symptoms such as cough, wheeze, shortness of breath, and chest tightness are not unique to asthma. They can indicate a range of acute or chronic diseases—including chronic obstructive pulmonary disease (COPD), pneumonia, gastroesophageal reflux disease (GERD), anxiety, and vocal cord dysfunction. Even non-respiratory conditions can mimic asthma, making objective testing vital for accurate diagnosis

The Four Pillars of Respiratory Diagnosis

This case study highlights the importance of addressing all four pillars of respiratory diagnosis:

1. Clinical Symptoms
2. Airway Obstruction
3. Inflammation
4. Airway Hyperresponsiveness

While patient history and physical examination provide valuable information, symptom overlap among asthma mimics means these alone are not enough. Objective tests—including spirometry, bronchial challenge, and inflammation assessment—are essential for a confident diagnosis.

Case Study: When Asthma Isn’t the Answer

Patient Profile:
A 64-year-old male presents with shortness of breath while on prednisone. His symptoms worsen when the dose drops below 10 mg daily. He is currently taking an inhaled corticosteroid (ICS) plus a long-acting beta2 agonist (LABA).

Pillar 1: Clinical Symptoms

• Non-atopic, never smoked
• Shortness of breath persists despite treatment

Pillar 2: Airway Obstruction

• Spirometry: Forced expiratory volume in one second (FEV1) before bronchodilator is 62% of predicted value; no improvement after bronchodilator
• Vital Capacity (VC): 64%
• FEV1/VC Ratio: 78%
• Diffusing Capacity of the Lungs for Carbon Monoxide (DLCO): 65%
• Carbon Monoxide Transfer Coefficient (KCO): 90%
• Total Lung Capacity (TLC): 65%

Pillar 3: Inflammation

• Blood eosinophils: 500 cells/µL
• Fractional exhaled nitric oxide (FeNO): 24 ppb (normal for adults)

Despite treatment, there is no bronchodilator responsiveness and no clear evidence of airway inflammation. Sputum eosinophils would be ideal but are difficult to collect. FeNO measurement provides a non-invasive assessment of T2 airway inflammation, but in this case, the result is normal. Further evaluation is warranted.

Pillar 4: Airway Hyperresponsiveness

• Methacholine challenge with Provocholine®: PC20 >16 mg/ml (negative result)

The negative methacholine challenge supports ruling out asthma.

The Real Diagnosis—and the Lesson

This patient does not have asthma yet was being treated for it and exposed to unnecessary medications. Unable to wean off prednisone without worsening symptoms, he was referred for further testing—including imaging and a sniff test. The final diagnosis: diaphragm myopathy. After corrective surgery, he no longer required ICS/LABA or oral prednisone.

Key Takeaways for Clinicians

• Don’t rely solely on symptoms: Many conditions mimic asthma.
• Use all four pillars: Objective testing—spirometry, inflammation assessment, bronchial challenge—provides confidence in diagnosis.
• Protect your patients: Accurate diagnosis prevents unnecessary treatment, financial burden, and side effects.
• Stay vigilant: Even when it looks and sounds like asthma, confirm with objective tests before starting therapy.

Author:

Heather Murgatroyd, BA, RRT, CPFT, AE-C 

Senior Clinical Specialist 

Methapharm Respiratory 

Acknowledgment:
This case study was contributed by a qualified pulmonologist and is presented in an anonymized form to maintain confidentiality.

References

1. S.D. Aaron, K.L. Vandemheen, et al. Reevaluation of Diagnosis in Adults with Physician-Diagnosed Asthma. JAMA. 2017;317(3):269-279.
2. Expert Panel Report 3 (EPR-3): Guidelines for the Diagnosis and Management of Asthma—Summary Report 2007. J Allergy Clin Immunol. 2007;120(5 Suppl):S94-138.
3. PROVOCHOLINE® package insert, revised 2/2023.
4. S. Khatri, J. Laccarino, et al. (2021) American Thoracic Society Documents. An Official ATS Clinical Practice Guideline: Use of Fractional Exhaled Nitric Oxide to Guide the Treatment of Asthma.
5. A.L. Coates, J. Wanger, D.W. Cockcroft, et al. ERS technical standard on bronchial challenge testing: general considerations and performance of methacholine challenge tests. Eur Respir J. 2017;49.