LAUSR

This study aimed to validate the Japanese version of a dysphagia-specific quality of life questionnaire, the MD Anderson Dysphagia Inventory (MDADI-J), and to verify trends between MDADI-J and Functional Oral Intake Scale (FOIS) scores. The original 20 MDADI items were translated using a forward–backward method following accepted cultural adaptation guidelines. Seventy-two patients with a history of head and neck cancer treatment completed the MDADI-J between October 2015 and August 2016. Concurrent validity was determined by correlations with the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30) and the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Head and Neck 35 (EORTC QLQ-H&N35) instruments. Discriminant validity was examined using cancer stage grouping between stages I–II and III–IV. Additionally, trends between the FOIS and the MDADI-J total scores were analyzed using a trend test. The Cronbach’s α coefficient of the MDADI-J total score was 0.92, indicating high internal consistency. The average inter-item correlation coefficients ranged from 0.39 to 0.49. ICC, an indicator of test–retest reliability, was 0.84 for the total score, and 0.58 to 0.81 for individual subscales. The total score and all subscales were significantly associated with the scores for each factor of the EORTC QLQ-C30 and EORTC QLQ-H&N35. The total score and all subscales were significantly different between clinical tumor stages I–II and III–IV. The total scores all increased with the progress of the FOIS. In conclusion, this study validated the Japanese version of the MDADI and showed that as FOIS scores deteriorate, MDADI-J scores tend to constantly decrease.