Item and response-category functioning of the Persian version of the KIDSCREEN-27: Rasch partial credit model

BACKGROUND The purpose of the study was to determine whether the Persian version of the KIDSCREEN-27 has the optimal number of response category to measure health-related quality of life (HRQoL) in children and adolescents. Moreover, we aimed to determine if all the items contributed adequately to their own domain. FINDINGS The Persian version of the KIDSCREEN-27 was completed by 1083 school children and 1070 of their parents. The Rasch partial credit model (PCM) was used to investigate item statistics and ordering of response categories. The PCM showed that no item was misfitting. The PCM also revealed that, successive response categories for all items were located in the expected order except for category 1 in self- and proxy-reports. CONCLUSIONS Although Rasch analysis confirms that all the items belong to their own underlying construct, response categories should be reorganized and evaluated in further studies, especially in children with chronic conditions.