Evaluation of chronic cough - Differentials | BMJ Best Practice US
frequent throat clearing, postnasal drip, nasal discharge, nasal obstruction or sneezing typical, halitosis
mucopurulent secretions in the nasopharynx and oropharynx or cobblestone appearance of posterior oropharynx
response to empiric therapy with antihistamine and decongestant
wheezing, chest tightness, dyspnea, symptom variability, strong family history of asthma/atopic disease, cough, paroxysms, exacerbation by irritants or seasonal exposures; cough may sometimes be the principal or sole symptom, usually worse at night (cough-variant asthma)
wheezing and prolonged expiratory phase on pulmonary exam
FEV1/forced vital capacity (FVC) ratio: below the lower limit of normal (LLN; if available) or <70% (if LLN not available) is positive for airflow obstruction; BDR test: improvement in FEV1 of 12% or more in response to beta agonists (or to a treatment trial with corticosteroids), together with an increase in volume of 200 mL or more is positive for reversibility of airway obstruction
may be reduced; may be variability (>10%) of measurements recorded at different times of the day
improvement in symptoms following a 2-4 week course of an inhaled corticosteroid or a leukotriene receptor antagonist
provocative concentration of methacholine causing a 20% fall in FEV1 (PC20) <4 mg/mL