Similarities and differences in assessing nausea on a verbal category scale and a visual analogue scale

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Abstract
The use of verbal category scales in assessing patient symptoms is evolving, but the extent to which reliability and precision are lost in using them as opposed to a visual analogue scale (VAS) remains uncertain. The present study analyzed the concordance between a four-point verbal category scale and a VAS in assessing nausea intensity in patients undergoing chemotherapy. The analysis of a total of 348 simultaneous ratings by 104 women over four cycles revealed good concordance between the scales. The means of the VAS ratings (range 0-100 mm) corresponding to the four verbal categories divided the scale in four almost equally large parts (no nausea = 0.7, mild = 24.8, moderate = 48.3, severe = 75.1). However, the VAS ranges were wide. On an individual level a one-step change in the verbal category was associated with an average change of 20 mm on the VAS. The choice of scale to use should be based on the need in the particular situation. When measuring intensity of nausea in patients, the VAS is a reasonable choice due to its possibly greater ability to detect changes over time. On the group level, findings on a four-point category scale and a VAS on the average seem similar.