Making the diagnosis of asthma

Common tests measure different aspects of the disease

Asthma is becoming more common in all parts of the world, and establishing the diagnosis is as important to clinical practitioners as it is to epidemiologists. For both the “gold standard” is still a clinical diagnosis based on a characteristic pattern of symptoms: episodes of cough, of dyspnoea, and of chest tightness or wheeze. The epidemiologist, however, wants further objective diagnostic tests to distinguish affected from unaffected people and then to compare populations and monitor trends. Most recent prevalence studies have relied on measurements of bronchial hyperresponsiveness to histamine or methacholine or to an exercise challenge as well as on tests of lung function. Toelle et al have proposed that for epidemiological purposes current asthma should be defined as appropriate symptoms in the previous 12 months together with evidence of increased airway responsiveness.1

The need for a clinician to use more specialised diagnostic testing is less clearly defined, but it may be summarised as the need to establish the diagnosis and assess the severity. International guidelines broadly agree on the management of established asthma, but they differ in their emphasis on confirmatory diagnostic testing. The British guidelines do not mention …