Determining correspondence between scores on the EQ-5D "thermometer" and a 5-point categorical rating scale.
BACKGROUND
"Feeling thermometers" and category rating scales (CRS) can be used to measure self-rated health, though the interpretation of scores on the feeling thermometer may be problematic.


OBJECTIVE
To analyze correspondence between scores of self-rated health on the EuroQol-5D "feeling thermometer" and a five-Point CRS. To determine the influence of sociodemographic variables on correspondence.


METHODS
Correspondence between EQ-5D "thermometer" scores and CRS categories was determined in a within-subjects design using data from a large-scale health survey.


METHODS
Twelve thousand, two hundred and forty-five members of the Spanish general population interviewed in the Catalan Health Interview Survey.


METHODS
Instruments used were the EQ-5D "feeling thermometer" and a five-Point CRS with categories from "excellent" to "poor."


RESULTS
Median scores on the thermometer corresponding to CRS categories were as follows: poor = 40; fair = 53; good = 76; and very good = 80; excellent = 90; differences were statistically significant (P < 0.05). Ranges in thermometer scores covered by CRS categories varied from 23.5 points for the category "poor" to 13 points for the category "very good" (range, 25-75 percentiles), with considerable overlap between categories at the upper end of the scale. Median thermometer scores corresponding to the categories "good,""fair," and "poor" were lower in older respondents and in those with a lower educational level.


CONCLUSIONS
Determining correspondence between CRS and thermometer scores is useful in interpreting and categorizing thermometer scores. The age and level of education in particular affect the interpretation of CRS categories, and should be taken into account when analyzing results obtained with such instruments.
Badia Llach
X
X
Institut de Salut Pública de Catalunya, Pavelló Central, Campus de Bellvitge, Universitat de Barcelona, L'Hospitalet, Spain. xbadia@bell.ub.es
Herdman
M
M
Schiaffino
A
A
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001294:Attitude to Health; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D004522:Educational Status; D005260:Female; D006296:Health Services / Q000706:statistics & numerical data; D006305:Health Status Indicators; D006801:Humans; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D015203:Reproducibility of Results; D012959:Socioeconomic Factors; D013030:Spain; D011795:Surveys and Questionnaires / Q000592:standards*