Assessing severity of asthma: spirometric correlates with visual analogue scale (VAS)

Measurements of dyspnoea in asthma are difficult. Peak expiratory flow (PEF) and forced expiratory volume in first second (FEV1) are the most widely used objective measures of bronchial obstruction in asthma. Subjective continuous scales like visual analogue scale (VAS) provide a more flexible means of grading dyspnoea as perceived by the patient.

Utility of a VAS in assessing severity of bronchial asthma was evaluated in 195 previously diagnosed adult patients with bronchial asthma. Patients were asked to mark their severity as perceived by them on a continuous vertical VAS of 100 mm anchored at bottom with description no breathlessness' and at top by 'greatest breathlessness'. The distance measured from bottom in mm was taken as VAS score. This was correlated with FEV1 and PEF recorded immediately after the scale was marked.

The mean VAS score was 31.13 (+/- 28.32) mm and had a good negative correlation with FEV1 (r = 0.5255, p < 0.01) and PEF (r = 0.4609, p < 0.01). Patients were also classified into four groups of mild, moderate, severe and acute asthma, and correlation analyzed in each group separately. The correlation was more significant in subgroups of moderate and severe asthma. Educational status of subjects had no impact on this correlation.

VAS is a reasonable tool for measurement and monitoring of severity of asthma in individual patients, and may be used when more objective tests are not available.