Background: Health-related quality of life (HRQoL) is a commonly used health outcome. For many acute conditions (e.g. fractures), retrospective measurement of HRQoL is necessary to establish pre-morbid health status. However, the validity of retrospective measurement of HRQoL following an intervening significant health event has not been established. The aim of this study was to test the validity of retrospective measurement (recall) of HRQoL by using a test-retest design to measure reliability and agreement between prospective and retrospective patient-reported HRQoL before and after an intervening health event (elective orthopaedic surgery).
Method: Participants were recruited from the pre-admission clinic of a metropolitan hospital. Participants were assessed for their HRQoL using the EQ-5D-5L at two time-points; prospectively at 2 weeks prior to their date of surgery and then retrospectively (recalling their pre-operative health) following elective hip or knee joint replacement surgery. Prospective measurements were compared with retrospective measurements for the five domain scores (nominal data) using intra-class correlation and for the EQ-Index score and EQ-Visual Analogue Scale (VAS) score (continuous data), using Pearson's correlation. Agreement was tested in continuous variables using Lin's coefficient of concordance (pc) and Bland-Altman plots.
Results: One hundred seventy-four patients consented to participate. Eighty-eight paired prospective and retrospective scores were collected and there was a median between-test period of 15 days. At a group level, the prospective measurements were similar to the retrospective measurements; the modes and means of the five domain scores were not different and the mean differences (MD) between the scores for EQ-Index (MD = 0.02, on a scale of 0-1) and EQ-VAS (MD = 0.53, on a scale of 1-100) were negligible. However, the correlation of paired scores was varied; the range of domain score correlations was 0.52 to 0.74, the concordance was substantial for the EQ-Index scores (pc = 0.76, 95% CI = 0.66, 0.84) and moderate for the EQ-VAS scores (pc = 0.46, 95% CI = 0.28, 0.61).
Conclusion: Agreement between prospective and retrospective measurements was high at a group level and moderate to substantial at an individual level. Retrospective measurement of HRQoL using the EQ-5D-5L in an orthopaedic clinical context is a valid alternative to using reference data to estimate baseline or pre-morbid health status.
Keywords: EQ-5D; Prospective; Quality of life; Reproducibility of results; Retrospective; Surveys and questionnaires; Test-retest reliability; Validity.