USING REFERENCE DATA ON QUALITY-OF-LIFE - THE IMPORTANCE OF ADJUSTINGFOR AGE AND GENDER, EXEMPLIFIED BY THE EORTC QLQ-C30 (+3)

Interpretation of health related quality of life (HRQOL) results in ca ncer patients is facilitated by knowledge of the levels of HRQOL in th e general population. However, direct comparisons can be misleading un less age and gender are considered. We demonstrate the derivation of a ge- and gender-specific 'expected' values from population reference va lues by means of simple calculations. This survey included 3000 random ly selected Norwegians above 18 years of age who received the European Organization for Research and Treatment of Cancer Core Quality of Lif e Questionnaire (EORTC QLQ-C30 (+ 3)) by mail. 1965 responses from 2,8 92 eligible persons (68%) were received. The population was divided in to six disease groups based on self-reported health problems. The obse rved mean scale scores of the different groups deviated greatly from t hose obtained in the general population. The score for physical functi on, for example, was 72 for cancer patients and ranged from 73.3 to 82 .5 in other disease groups, as opposed to 89.9 in the general populati on and 98.9 in those with no health problems. The range for one of the quality of life (QOL) scales was 57.7 to 84.7 compared with 73.7 in t he general population. Expected mean scores for the patient groups wer e computed from the reference values, based on the concept of equivale nce of age and gender. The differences between the observed mean score s and the reference values were strongly mediated by this method. The expected scores for physical function then ranged from 83.3 to 93.1 an d from 70.3 to 75 for the QOL scale. The impact of age and gender on t he reference data from the EORTC QLQ-C30 (+ 3) obtained in a general p opulation shows that these variables must be considered when interpret ing data on HRQOL for cancer patients. The demonstration of how to gen erate mean values which are adjusted according to the age and gender d istribution of a population should increase the usefulness of this que stionnaire among clinicians. (C) 1998 Elsevier Science Ltd. All rights reserved.