[Development of the Japanese version of the 16-Item Informant Questionnaire on Cognitive Decline for the Elderly (J-IQCODE 16) for the Diagnosis of Prestroke Dementia].

The 16-Item Informant Questionnaire on Cognitive Decline for the Elderly (IQCODE 16) has been frequently used to diagnose prestroke dementia, an important determinant of stroke prognosis. We developed the Japanese version of the IQCODE 16 (J-IQCODE 16) using standardized translation methods. We applied the J-IQCODE 16 to 102 patients with stroke (19 with prestroke dementia diagnosed with DSM-5) admitted to the stroke care unit in our hospital. The cohort was randomly divided into a derivation cohort and a validation cohort containing 51 patients each. In the derivation cohort, the median J-IQCODE 16 score was 3.06, and the area under the receiver operating characteristic curve for prestroke dementia was 0.96, with an optimal cutoff value of 3.25 determined using the Youden index. When applied this cut-point to the validation cohort, the sensitivity and specificity of the J-IQCODE 16 for prestroke dementia were 90% and 85%, respectively. The J-IQCODE 16 is considered useful for the diagnosis of prestroke dementia.