Criteria used to define the eight respiratory syndromes

SyndromeCriteriaTreatment and management relevant to the analysis
Fixed airflow limitation (COPD) without eosinophiliaPost-bronchodilator FEV1/FVC<lower limit of normal AND no eosinophilia# at presentationLong-acting bronchodilators, SABA [29]
Fixed airflow limitation (COPD) with eosinophilic inflammationPost-bronchodilator FEV1/FVC<lower limit of normal AND eosinophilia# at presentationLong-acting bronchodilators, ICS, SABA [29]
Reversible airflow limitation (asthma)FEV1 increases by >200 mL and >12% of the baseline value after inhaling a bronchodilatorICS, long-acting bronchodilators [30]
Other airflow limitationFEV1/FVC<lower limit of normal on baseline spirometry for those without measure of post-bronchodilator spirometryMay benefit from bronchodilators; consider post-bronchodilator spirometry
Lower respiratory tract infectionFocal or localised airspace consolidation on chest radiograph AND neutrophiliaAntibiotics
TuberculosisPositive GeneXpert result for sputum sampleAnti-tuberculosis agents
Heart failureCardiomegaly+ on chest radiograph AND one or more signs of pulmonary venous hypertension on chest radiograph OR elevated BNP/pro-BNP level§Diuretics for volume overload [31]
Upper respiratory tract infection (common cold)Moderate symptoms in at least 2 of the 4 categories, OR mild symptoms in 3 or more categories, OR mild symptoms in one category plus a cough in Common Cold Questionnaire [28] with symptoms last ≤10 days AND none of the above 7 syndromesSymptomatic treatment

FEV1: forced expiratory volume in 1 s; FVC: forced vital capacity; SABA: short-acting beta-agonists; ICS: inhaled corticosteroids; BNP: brain natriuretic peptide. #: eosinophil count >0.3×109 L−1 [29]; : neutrophil count >6.3×109 L−1 [32]; +: cardiothoracic ratio >0.55; §: BNP level >400 pg·mL−1, pro-BNP level >450 pg·mL−1 for subjects aged <50 years, pro-BNP level >900 pg·mL−1 for subjects aged 50–75 years, pro-BNP level >1800 pg·mL−1 for subjects aged >75 years [33].