Which questionnaire outcome of two different perspectives is most comparable with the self-completed questionnaire outcome when assessing the quality of life in orthopedic patients.

Rationale: There are two by proxy versions of the EQ-5D-5L questionnaire if the patient is not able to self complete the questionnaire. Currently there is no conclusive evidence which of these two by proxy versions reflects the self-completed EQ-5D-5L most accurately.

Objective: To compare the self-completed EQ-5D-5L questionnaire and its proxy versions in a population of adult orthopaedic patients at the outpatient clinic.

Study design: A randomised monocenter agreement study.

Study population: All orthopaedic patients of 18 years of older with no signs of cognitive impairment based on the judgement of the clinician, who are visiting the outpatient clinic with a relative.

Agreement study: The outcomes of the proxy-proxy and the proxy-patient version of the EQ-5D-5L questionnaire will be compared with the self-completed EQ-5D-5L questionnaire to estimate which by proxy version is superior.

Main study parameters/endpoints: The level of agreement between the outcomes of the self-completed EQ-5D-5L questionnaire and its proxy versions.

The proxy-patient perspective outcome has a higher level of agreement with the outcome of the self-completed EQ-5D-5L, compared with the proxy-proxy perspective outcome in mentally healthy patients.

The EQ-5D-5L questionnaire will be assessed at the Orthopaedic outpatient clinic. The patient and proxy giver should independently complete the questionnaire, without helping each other.

The EQ-5D-5L is a generic HRQoL measurement tool where respondents choose 1 of 5 descriptors in 5 domains of their health (mobility, personal care, usual activities, pain/discomfort, and anxiety/depression) followed by a Visual Analogue Scale (VAS) of their overall current health state.

Patients allocated to the proxy-proxy group A will receive the proxy A version of the EQ-5D-5L: The proxy giver is asked to rate the patient¡¯s health-related quality of life in their (the proxy¡¯s) opinion.

Patients allocated to the proxy-patient group B will receive the proxy B version of the EQ-5D-5L: The proxy giver is asked to rate how he/she (the proxy) thinks the patient would rate his/her own health-related quality of life if the patient were able to communicate it.