Accuracy of a first diagnosis of asthma in primary health care.
BACKGROUND: In a postal questionnaire study, the prevalence of asthma in southern Sweden has been found to be 5.5%. However, the register prevalence of asthma obtained from the medical records in the same municipality and age groups was found to be only 2.1%. OBJECTIVES: The aims of the study were to investigate whether the low register prevalence of asthma was caused by an underdiagnosis of asthm