Reliability and validity of the Korean version of the Functional Status Score for the ICU after translation and cross-cultural adaptation

Purpose The Functional Status Score for the Intensive Care Unit (FSS-ICU) evaluates the physical function of ICU patients. The objective of the study was to translate and cross-culturally adapt the FSS-ICU into Korean and assess its reliability and validity. Methods An expert committee supervised the forward and backward translation process and the final translated version. Experienced physiotherapists assessed patients (n= 31) from a medical ICU using the Korean version of FSS-ICU. Intra-class correlation coefficients (ICCs) and Bland-Altman's plots were used to evaluate reliability, and Cronbach's alpha for internal consistency. Construct validity was evaluated using Spearman's correlation coefficients. Results Two physiotherapists in each of the two university hospitals independently assessed 31 medical ICU patients, with a mean FSS-ICU total score of 23 (range: 4-35). The FSS-ICU Korean version demonstrated excellent internal consistency, with Cronbach's alpha of 0.897 for the total FSS-ICU score, and a range of 0.844-0.892 with deletion of each individual activity within the FSS-ICU. Intra-rater and inter-rater reliability were excellent for all of five FSS-ICU activities and the total score, with an ICC range of 0.930-0.993. Bland-Altman's plots revealed a mean difference in FSS-ICU total score of 0.2 (95% limits of agreement: -1.9 to 2.3) between two physiotherapists. The Korean version of FSS-ICU had good convergent and divergent validity with moderate to strong correlation with mobility and muscle strength measures, and poor correlation with unrelated measures. Conclusions The Korean version of the FSS-ICU showed excellent intra-rater and inter-rater reliability, internal consistency, and construct validity for medical ICU patients. The results of this study, along with prior publications, support that the FSS-ICU Korean version is a valid and reliable assessment tool for the ICU environment.Implications for rehabilitationIntensive care unit patients usually experience decreased muscle strength and physical function.The Korean version of the Functional Status Score for the Intensive Care Unit (FSS-ICU) is suitable for use with Korean speakers and has a valid, reliable measurement tool for physical function of intensive care unit patients.A well-standardized training with videos and written materials is important to ensure correct implementation of the Korean version of the FSS-ICU.