Perils of asthma research in vulnerable groups.
D000367:Age Factors; D000368:Aged; D000375:Aging; D001249:Asthma / Q000150:complications / Q000188:drug therapy; D002648:Child; D015897:Comorbidity; D018432:Drug Resistance, Multiple; D006801:Humans; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000188:drug therapy; D035842:Research Subjects; D012129:Respiratory Function Tests; D035862:Vulnerable Populations