International consensus guidelines have recently been developed to improve the assessment and management of asthma. One of the major recommendations of these guidelines is that asthma severity should be assessed through the recognition of key symptoms, such as nocturnal waking, medication requirements, and objective measurements of lung function. Differential classification of asthma severity would lead to major differences in both long term pharmacological management and the treatment of severe exacerbation.

This study examined the relationship between the symptom score and measurements of FEV1 and PEF when expressed as a percentage of predicted values in asthmatics(n=107).

The correlation of FEV1% with PEFR% was highly significant(r=0.83,p<0.01). However, there was agreement in terms of the classification of asthma severity in 76.6% of the paired measurements of FEV1% and PEFR%. Agreement in the classification of asthma severity was also found in 57.1% of the paired analysis of FEV1% and symptom score. 39% of the patients classified as having moderate asthma on the basis of FEV1% recording would be considered to have severe asthma if symptom score alone were used. Low baseline FEV1 and high bronchial responsiveness were associated with a low degree of perception of airway obstruction.

The relationships between the symptom score, PEFR and FEV1 were generally poor. When assessing asthma severity, age, duration, PC20, and baseline FEV should be considered.