Initial development of a patient-reported outcome measure of disability due to Katakori via evaluating patient comprehensibility and comprehensiveness

[Purpose] “Katakori” refers to a nonspecific symptom, including discomfort or dull pain, that is experienced around the occiput and that extends through the cervical spine to the acromion and scapular area. This study aimed to develop a patient-reported outcome measure of disability due to Katakori, namely the Katakori Disability Index, via evaluating patient comprehensibility and comprehensiveness. [Participants and Methods] We conducted a semi-structured interview among participants who had experienced Katakori consistently during the past month to examine patient comprehensibility and comprehensiveness; we particularly used the thinking-aloud method and cognitive debriefing to evaluate comprehensibility. [Results] We initially tested a provisional version of the Katakori Disability Index with 24 items using two 11-point numeric rating scales in a subset of 10 participants. Considering the issues identified concerning comprehensibility and comprehensiveness, we created a second draft of the Katakori Disability Index with two 6-point Likert scales, modified items, and four additional items. The second draft was tested in another subset of 10 participants. We eventually developed a 31-item Katakori Disability Index with modified instructions and items, two additional items, and a post-survey checklist; all these features addressed the concerns identified and suggestions obtained in the second round of interviews. [Conclusion] We developed a 31-item Katakori Disability Index with content validity.