Measurement of dyspnea: word labeled visual analog scale vs. verbal ordinal scale

We previously used a verbal ordinal rating scale to measure dyspnea. That scale was easy for subjects to use and the words provided consistency in ratings. We have recently developed a word labeled visual analog scale (LVAS) with labels placed by the subjects, retaining the advantages of a verbal scale while offering a continuous scale that generates parametric data. In a retrospective meta-analysis of data from 43 subjects, individuals differed little in their placement of words on the 100 mm LVAS (mean+/-S.D. for slight=20+/-2.5 mm, moderate=50+/-5 mm and severe=80+/-6 mm) and ratings were distributed uniformly along the scale. A significant stimulus-response correlation was obtained for both the LVAS (r(2)=0.98) and for the verbal ordinal scale (Spearman r=0.94). The resolution of the two scales differed only slightly. With meaningful verbal anchors, well-defined end-points, and clear instructions about the specific sensation to be rated, both scales provide valid measures of dyspnea.