An 8-year-old girl is brought to the clinic due to a prolonged cough. The patient developed rhinorrhea 6 weeks ago, followed a week later by a cough with occasional expectoration of whitish sputum; the rhinorrhea resolved at that time. For the past 5 weeks, the patient's cough has continued without improvement throughout the day and night, occasionally awakening her. Use of a humidifier has not relieved her symptoms. The patient has been afebrile and has had no vomiting, abdominal pain, diarrhea, or sick contacts. She takes no daily medications. Immunizations are up to date. Family history is notable for atopic dermatitis in the mother. Height and weight are tracking at the 25th percentile. Temperature is 36.7 C (98 F) and respirations are 24/min. The patient is awake, alert, and playing. Tympanic membranes are normal. The tonsils are normal. The mucous membranes are moist, and the lips are pink. Heart rate and rhythm are normal. The lungs are clear to auscultation bilaterally; no retractions or use of accessory chest muscles is present. Which of the following is the best next step in diagnosis?
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This patient has chronic cough, which is defined as daily cough lasting >4 weeks in children (>8 weeks in adults). Initial evaluation includes a thorough history and physical examination to look for a specific underlying cause and guide management. For example, a history of choking preceding symptom onset may suggest an aspirated foreign body, and poor growth may suggest a chronic illness (eg, cystic fibrosis [CF]).
In the absence of specific findings, the first step in evaluation is spirometry. This simple pulmonary function test can assess for asthma, a common cause of chronic cough in children. Although asthma may be associated with other findings (eg, wheezing, dyspnea, history of atopy), it can present with cough alone and a normal examination, as in this case.
Spirometry can be performed in a cooperative child (generally age >6) and, in asthma, it shows an obstructive pattern (due to bronchial inflammation and smooth muscle contraction) that is reversible with a bronchodilator (eg, albuterol). Symptom improvement following a 2-week trial of a short-acting beta agonist and inhaled corticosteroid is confirmatory. This trial can be conducted empirically (ie, without spirometry) in children unable to perform spirometry.
(Choice A) If spirometry is unrevealing or an empiric bronchodilator trial fails, then chest x-ray is performed to evaluate for abnormalities such as foreign body aspiration (eg, unilateral hyperinflation). CT scan of the chest may be considered if x-ray is nondiagnostic but is not preferred for initial imaging due to radiation exposure.
(Choice B) Although pertussis can lead to chronic cough, it is less likely in this vaccinated child with no classic historical findings of pertussis (eg, paroxysmal cough, inspiratory whoop). Spirometry and imaging should be performed first in this patient; testing for Bordetella pertussis may be considered if these studies are unrevealing.
(Choice D) Sputum culture can be obtained for chronic cough due to suspected chronic pulmonary infection (eg, mycobacterial, fungal). However, fungi and nontuberculous mycobacteria typically affect immunocompromised patients, and this child has no other symptoms (eg, fever, weight loss) of tuberculosis.
(Choice E) Sweat chloride testing is used in the evaluation of CF, which typically causes failure to thrive (weight below the 2nd percentile or decreasing by ≥2 major percentiles) and pancreatic insufficiency (eg, steatorrhea) in addition to pulmonary disease (eg, recurrent pneumonia). In contrast, this patient has an isolated cough, normal growth curves, and no diarrhea, making CF unlikely.
Educational objective:
Chronic cough (>4 weeks in children) without specific historical or examination findings is commonly due to asthma, and the first step in evaluation is spirometry.