Impact of the occurrence of a response shift on the determination of the minimal important difference in a health-related quality of life score over time.

Ahmad Ousmen,Mariette Mercier,Franck Bonnetain,Olivier Graesslin,Francis Guillemin,Amélie Anota,Michel Velten,Sylvain Causeret,Thierry Conroy,Zeinab Hamidou,Jean Cuisenier,Damien Jolly

doi:10.1186/s12955-016-0569-5

Abstract

BackgroundAn important challenge of the longitudinal analysis of health-related quality of life (HRQOL) is the potential occurrence of a Response Shift (RS) effect. While the impact of RS effect on the longitudinal analysis of HRQOL has already been studied, few studies have been conducted on its impact on the determination of the Minimal Important Difference (MID). This study aims to investigate the impact of the RS effect on the determination of the MID over time for each scale of both EORTC QLQ-C30 and QLQ-BR23 questionnaires in breast cancer patients.MethodsPatients with breast cancer completed the EORTC QLQ-C30 and the EORTC QLQ-BR23 questionnaires at baseline (time of diagnosis; T0), three months (T1) and six months after surgery (T2). Four hospitals and care centers participated in this study: cancer centers of Dijon and Nancy, the university hospitals of Reims and Strasbourg At T1 and T2, patients were asked to evaluate their HRQOL change during the last 3 months using the Jaeschke transition question. They were also asked to assess retrospectively their HRQOL level of three months ago.The occurrence of the RS effect was explored using the then-test method and its impact on the determination of the MID by using the Anchor-based method.ResultsBetween February 2006 and February 2008, 381 patients were included of mean age 58 years old (SD = 11). For patients who reported a deterioration of their HRQOL level at each follow-up, an increase of RS effect has been detected between T1 and T2 in 13/15 dimensions of QLQ-C30 questionnaire, and 4/7 dimensions of QLQ-BR23 questionnaire. In contrast, a decrease of the RS effect was observed in 8/15 dimensions of QLQ-C30 questionnaire and in 5/7 dimensions of QLQ-BR23 questionnaire in case of improvement. At T2, the MID became ≥ 5 points when taking into account the RS effect in 10/15 dimensions of QLQ-C30 questionnaire and in 5/7 dimensions of QLQ-BR23 questionnaire.ConclusionsThis study highlights that the RS effect increases over time in case of deterioration and decreases in case of improvement. Moreover, taking the RS into account produces a reliable and significant MID.Electronic supplementary materialThe online version of this article (doi:10.1186/s12955-016-0569-5) contains supplementary material, which is available to authorized users.

Highlights

An important challenge of the longitudinal analysis of health-related quality of life (HRQOL) is the potential occurrence of a Response Shift (RS) effect
This study demonstrated that the recalibration component of the RS effect does not have an important effect in patients with multiple myeloma who respond to treatment, i.e. for which a HRQOL improvement was observed
We looked at the direction of the RS effect: a positive value of RS indicates that patients had overestimated their HRQOL level, their functional or symptomatic level at the previous measurement time

Summary

Introduction

An important challenge of the longitudinal analysis of health-related quality of life (HRQOL) is the potential occurrence of a Response Shift (RS) effect. For the European Organization of Research and Treatment of Cancer (EORTC) HRQOL questionnaires, the MID is generally fixed to 5 or 10 points for each score standardized on a 0–100 scale [2]. This MID must be studied and determined for each HRQOL questionnaire and according to each cancer site. This was already made for the EORTC module of lung and brain cancer as example [7, 8]. Patients may not assess with the same criteria their HRQOL level over time

Objectives

Methods

Results

Conclusion