Protocol for the field-test and psychometric validation of the pectus excavatum evaluation questionnaire in the Dutch pectus excavatum population

Background: Pectus excavatum severely impacts health-related quality of life of affected individuals. The most widely used disease-specific instrument for assessing health-related quality of life in this population is the pectus excavatum evaluation questionnaire (PEEQ). As originally developed and field-tested in the United States, the PEEQ may not be directly applicable in other countries or non-English speaking populations. Here, we outline a protocol for the field-test and psychometric validation of the Dutch translation of the PEEQ. Methods: This prospective single-center study will field-test and validate the psychometric properties of the Dutch PEEQ in sixty-six pectus excavatum patients aged 12 to 17 years old who are scheduled for a Nuss procedure. Their parents/legal guardian will fill out the adult section of the questionnaire. Psychometric validation includes the evaluation of structural validity, internal consistency, test-retest validity, responsiveness, floor- and ceiling effects, and the smallest detectable change. Discussion: As a tertiary referral center, our institution attracts patients from across the Netherlands, enhancing the representativeness of the study sample. To maintain internal validity and focus on clinically significant deformities, the study excludes certain subgroups, including younger children, adults, and those treated conservatively or with the Ravitch procedure. While postoperative responsiveness is assessed, the long-term responsiveness of the PEEQ is not addressed. Despite these limitations, this study represents an important step in validating the PEEQ for clinical and research purposes.