Development of a screening tool for risk of locomotive syndrome in the elderly: the 25-question Geriatric Locomotive Function Scale

To evaluate the reliability and validity of a new questionnaire, the 25-question Geriatric Locomotive Function Scale (GLFS-25), for early detection of locomotive syndrome. This new screening tool was designed to detect Japanese individuals under high-risk conditions who may soon require care services because of problems of the locomotive organs. Content validity, construct validity, criterion validity, internal-consistency reliability, and reproducibility (test-retest reliability) were examined using psychometric analysis, and a cutoff score to detect locomotive syndrome was determined. To investigate construct validity of the GLFS-25 and determine the cutoff score, the Akaike Information Criteria (AIC) were used. Study 1 analyzed 711 Japanese elderly people ≥65years old. No floor or ceiling effects were included in the GLFS-25. Internal consistency was confirmed by a Cronbach’s α reliability coefficient of 0.961. As for the association between the GLFS-25 and European Quality of Life Scale-5 Dimensions (EQ-5D), Spearman’s correlation coefficient was 0.85 (P < 0.001), showing excellent concurrent validity of the GLFS-25. Categorical principal component analysis showed that the construct structure consisted of one item cluster or the GLFS-25 was unifactorial. The AIC showed that one cluster of seven items was located in the center, with significant associations with the other five clusters. In study 2, 205 individuals were analyzed, and the test-retest interclass correlation was satisfactory (range 0.712–0.924). The cutoff score for identifying locomotive syndrome was set at 16. Validity and reliability of this new measurement were psychometrically confirmed as sufficient. The GLFS-25 offers a valid and reliable questionnaire scale for detecting locomotive syndrome in elderly Japanese individuals.