Development of a Japanese version of the Pain Disability Index: translation and linguistic validation

The Pain Disability Index ( PDI ) is a self–reported outcome measure initially developed in English to assess disability caused by pain in seven dimensions of daily life activity, including family ⁄ home responsibilities, recreation, social activity, occupation, sexual behavior, self–care, and life–support activity. This study aimed to develop a linguistical ly valid Japanese version of the PDI ( PDI–J ) according to the guidelines for the translation and cultural adaptation of patient–reported outcome measures establish ed by the task force of the International Society for Pharmacoeconomics and Outcomes Research. A draft of the PDI–J was developed through a forward translation of the original PDI from English to Japanese, reconciliation of the translation, back– translation from Japanese to English, and harmonization. We subsequently conducted a cognitive debriefing in five patients using the PDI–J draft and reviewed it before finaliz ing a linguistically valid PDI–J. We also considered a five–item version of the PDI ( PDI–5–J ) , which excluded two items ( sexual behavior and life–support activity ) from the original version. This consideration was made for brevity and because sexual behavior is a considerably personal parameter that some patients may be reluctant to answer and life–support activity because it was considered ambiguous in Japanese. Therefore, we were able to develop a linguistically valid PDI–J and PDI–5–J through this process. Further study is warranted to confirm the psychometric validity and reliabili ty of the two indices