Electronic supplementary material
The online version of this article (https://doi.org/10.1186/s12955-018-0905-z) contains supplementary material, which is available to authorized users.
The Diabetes Quality-of-Life (DQOL) Measure is a 46-item diabetes-specific quality of life instrument. The original English version of the DQOL has been translated into Chinese after cultural adaption, and the Chinese DQOL has been validated in the Chinese diabetic patient population and used in diabetes-related studies. There are two recognized problems with the Chinese DQOL: 1) the instrument is too long, and 2) the non-response rate of certain items is relatively high. This study aimed to develop and validate a short version for the Chinese DQOL.
Item reduction was conducted based on the classical test theory (CTT) and item response theory (IRT), each combined with exploratory factor analysis (EFA). The confirmatory factor analysis (CFA) and Spearman correlation coefficient were employed in validating the short versions.
Both the study sample (n = 2,886) and the validation sample (n = 2,286) were from a longitudinal observation study of Chinese type 2 diabetic patients. The CTT kept 32 items, and the IRT kept 24 items from the original 46-item version. The two short versions were comparable in psychometric properties.
The 24-item IRT-based short version of the Chinese DQOL was selected as the preferred short version because it imposes a lower burden on patients without compromising the psychometric properties of the instrument.