A 32-year-old woman is evaluated for a 6-month history of nonproductive cough. She has no history of recurrent upper respiratory tract infections and has never smoked cigarettes. She has no fever, dyspnea on exertion, hemoptysis, heartburn, or wheezing. She has worked in the same office for 7 years and has lived in the same house for the past 20 years. She has not traveled out of the area for more than 2 years. She has no pets at home, no occupational or other exposure to toxic chemicals, and no family history of pulmonary disease. She takes no medications.
The vital signs and results of the physical examination are normal. A complete blood count with differential is normal. Chest radiograph is normal. Pulmonary function tests are normal and a methacholine challenge test is negative.
Which of the following is the most appropriate diagnostic test to perform next?
B: 24-hour esophageal pH manometry
C: Sinus imaging
D: Sputum testing for eosinophils
MKSAP Answer and Critique
The correct answer is D: Sputum testing for eosinophils.
This patient’s presentation is consistent with nonasthmatic eosinophilic bronchitis (NAEB), and the next diagnostic step would be sputum testing for eosinophils. NAEB is an increasingly recognized cause of chronic cough, particularly in patients such as this one who lack risk factors or findings for the more common causes of chronic cough (smoking, cough-variant asthma, gastroesophageal reflux disease, upper airway disease). Patients with NAEB do not exhibit symptoms of or pulmonary function testing evidence of airflow obstruction or hyperresponsiveness, with or without provocation with methacholine, which differentiates this entity from asthma. The diagnosis is supported by airway eosinophilia in an induced sputum sample (greater than 3%), bronchial washings, or biopsy. Although bronchial mucosal biopsies are required to definitively diagnose eosinophilic bronchitis, most experts recommend a therapeutic trial of inhaled corticosteroid therapy as initial therapy, as most patients with NAEB will respond to this intervention.
Targeted and optimized empiric treatment of common causes of chronic cough is generally recommended prior to more invasive or costly testing. Treatment with antihistamines or decongestants should begin first, without need for sinus radiographs to evaluate for sinus disease in patients with suspected upper airway cough syndrome. Similarly, diet and lifestyle modification plus proton-pump inhibitors for 1 to 3 months should be prescribed prior to considering 24-hour esophageal pH manometry to evaluate for acid reflux disease.
- A diagnosis of nonasthmatic eosinophilic bronchitis should be considered in patients with chronic, nonproductive cough without an apparent cause, including asthma; sputum examination for eosinophils is useful in establishing the diagnosis.
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