Validation of a proxy‐reported SARC‐F questionnaire for current and retrospective screening of sarcopenia‐related functional impairments

Background: The strength, assistance walking, rise from a chair, climb stairs, and falls (SARC-F) questionnaire is a well-established instrument for screening of sarcopenia and sarcopenia-related functional impairments. As it is based on self-reporting, its use precludes patients who are unable to answer the questionnaire as a consequence of severe acute diseases or cognitive impairment. Therefore, we aimed to validate a proxy-reported version of the SARC-F for both ad-hoc as well as retrospective screening for severe sarcopenia-related functional impairments. Methods: Patients aged ≥60 years completed the SARC-F and performed the short physical performance battery (SPPB) at baseline (T1). Proxies in Cohort A gave a simultaneous assessment of the patients' functional status with the proxy-reported SARC-F at T1 and again, retrospectively, after 3 months (T2). Proxies in Cohort B only completed the SARC-F retrospectively at T2. The questionnaires' performances were assessed through sensitivity/specificity analyses and receiver operating characteristic (ROC) curves. For non-inferiority analyses, results of both the patient-reported and proxy-reported SARC-F were correlated with the SPPB total score as well as the results of the chair-rise test subcategory; the respective correlation coefficients were tested against each other. Results: One hundred and four patients and 135 proxies participated. Using a SPPB score