Reliability testing of the Danish version of the Kidney Disease Quality of Life Short Form

The questionnaire Kidney Disease Quality of Life Short Form version 1.3 (KDQOL-SF) is valuable for assessing the health-related quality of life in patients treated with chronic dialysis. The aim of this study was to translate and test the reliability of the KDQOL-SF for use in Denmark.

Translation into Danish and back-translation into English were performed. Pilot, field and internal consistency reliability tests were performed.

Cronbach's alpha coefficients for the internal reliability test ranged from 0.77 to 0.93 for the eight generic scales. In a test involving all patients, two of the disease-specific scales had Cronbach's alpha coefficients of <0.70 ("social support" = 0.67; and "quality of social interaction" = 0.43). After removing one item from the scale "quality of social interaction", Cronbach's alpha reached 0.63. A test of the scores of peritoneal dialysis (PD) patients discovered low reliability for three disease-specific scales. The KDQOL-SF manual and the Danish manual for the Short Form 36 (SF36) differed in the scoring of four generic scales: "role limitation-physical", "bodily pain", "general health" and "social function".

With the exception of the scale "quality of social interaction" the Danish translation of the KDQOL-SF achieved values in the internal consistency reliability test of the same level as the original U.S. version. When data were stratified according to dialysis treatment, the reliability of PD patients scores was lower. Generic data from the questionnaire SF36 should be scored according to the Danish SF36 manual.