*Purpose: Though kidney transplant is the optimal treatment for most individuals with end stage kidney disease, recipients experience significant side effects associated with their required daily use of multiple immunosuppressive medications, which may diminish the benefits of transplant. Especially common and burdensome are neurological side effects of calcineurin-inhibitors (CNIs), such as tacrolimus. These medications can cause tremors, headache, and difficulties with memory and concentration. To date, there is little research to develop and validate patient reported outcome (PRO) measures appropriate for immunosuppression trials with kidney transplant recipients.

*Methods: We conducted concept elicitation interviews with 12 participants (kidney transplant recipients) about their experience of side effects from CNIs. These concept elicitation data informed the construction of a new PRO using items developed and validated for use in common neurological conditions sourced from Neuro-QOL and FACIT item banks. We then conducted cognitive debriefing interviews with an additional 14 participants to assess the relevancy and clarity of a novel PRO measure designed to capture CNI side effect burden.

*Results: In the concept elicitation interviews, 83% of participants described neurological side effects. The most commonly described side effect was hand tremors (59%), followed by difficulties with cognition and memory (45%), headaches (29%) and numbness or tingling in the extremities (25%). In the cognitive interviews, participants reported understanding the PRO items 99.5% of the time. Participants described items as relevant to their experiences of neurological side effects 64% of the time. Several patients (7/14) felt the term “tremor” did not represent their experience; instead, they preferred the term “shaky hands”. This led to three new items measuring the impact and bother of shaky hands. The resultant PRO measure consists of 13 items representing 5 domains—tremors, paresthesia, headache, cognition, and physical function.

*Conclusions: This effort established the content validity of a new PRO measure focused on CNI side effects. We also demonstrated the relevance and clarity of the items included in this new 13-item measure. Future research includes a quantitative validation study to finalize this measure in an effort to advance CNI tolerability assessments in future clinical trials.

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