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. 2018 Jun 26;16(1):130.
doi: 10.1186/s12955-018-0950-7.

Assessing health status over time: impact of recall period and anchor question on the minimal clinically important difference of copd health status tools

H J Alma  1   2 , C de Jong  3   4 , D Jelusic  5 , M Wittmann  5 , M Schuler  6 , B J Kollen  3 , R Sanderman  7   8 , K Schultz  5 , J W H Kocks  3   4 , T Van der Molen  3   4
Affiliations

Assessing health status over time: impact of recall period and anchor question on the minimal clinically important difference of copd health status tools

H J Alma et al. Health Qual Life Outcomes. .

Abstract

Background: The Minimal Clinically Important Difference (MCID) assesses what change on a measurement tool can be considered minimal clinically relevant. Although the recall period can influence questionnaire scores, it is unclear if it influences the MCID. This study is the first to examine longitudinally the impact of the recall period of an anchor question and its design on the MCID of COPD health status tools using the COPD Assessment Test (CAT), Clinical COPD Questionnaire (CCQ) and the St. George's Respiratory Questionnaire (SGRQ).

Methods: Moderate to very severe COPD patients without respiratory co-morbidities were recruited during 3-week Pulmonary Rehabilitation (PR). CAT, CCQ and SGRQ were completed at baseline, discharge, 3, 6, 9 and 12 months. A 15-point Global Rating of Change scale (GRC) was completed at each follow-up. A five-point GRC was used as second anchor at 12 months. Mean change scores of a subset of patients indicating a minimal improvement on each of the anchor questions were considered the MCID. The MCID estimates over different time periods were compared with one another by evaluating the degree of overlap of Confidence Intervals (CI) adjusted for dependency.

Results: In total 451 patients were included (57.9 ± 6.6 years, 65% male, 50/39/11% GOLD II/III/IV), of which 309 completed follow-up. Baseline health status scores were 20.2 ± 7.3 (CAT), 2.9 ± 1.2 (CCQ) and 50.7 ± 17.3 (SGRQ). MCID estimates for improvement ranged - 3.1 to - 1.4 for CAT, - 0.6 to - 0.3 for CCQ, and - 10.3 to - 7.6 for SGRQ. Absolute higher - though not significant - MCIDs were observed for CAT and CCQ directly after PR. Significantly absolute lower MCID estimates were observed for CAT (difference - 1.4: CI -2.3 to - 0.5) and CCQ (difference - 0.2: CI -0.3 to -0.1) using a five-point GRC.

Conclusions: The recall period of a 15-point anchor question seemed to have limited impact on the MCID for improvement of CAT, CCQ and SGRQ during PR; although a 3-week MCID estimate directly after PR might lead to absolute higher values. However, the design of the anchor question was likely to influence the MCID of CAT and CCQ.

Trial registration: RIMTCORE trial # DRKS00004609 and #12107 (Ethik-Kommission der Bayerischen Landesärztekammer).

Keywords: COPD assessment test (CAT); Chronic obstructive pulmonary disease (COPD); Clinical COPD questionnaire (CCQ); Clinically relevant change; Global rating of change scale; Health status; Minimal clinically important difference; Pulmonary rehabilitation; Recall period; St. George’s respiratory questionnaire (SGRQ).

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Conflict of interest statement

Ethics approval and consent to participate

This study is a secondary analysis of a subsample from the Routine Inspiratory Muscle Training within COPD Rehabilitation (RIMTCORE) real-life randomized controlled trial (#DRKS00004609) in the Klinik Bad Reichenhall, Center for Rehabilitation, Pulmonology and Orthopaedics in Germany. All patients signed informed consent upon participation. The RIMTCORE trial was approved by the Ethik-Kommission der Bayerischen Landesärztekammer (#12107) and registered in the German Clinical Trial Register.

Consent of publication

All authors participated in various steps in the study, edited the manuscript and gave their approval for submission.

Competing interests

H.J. Alma, C. de Jong, D. Jelusic, M. Wittmann, M. Schuler, B.J. Kollen and R. Sanderman have nothing to disclose. J.W.H. Kocks reports personal fees from Novartis; research grants and personal fees from Boehringer Ingelheim; research grants and personal fees from GSK; research grants from Stichting Zorgdraad; personal fees from IPCRG; personal fees from Springer Media; and travel arrangements from Chiesi BV, GlaxoSmithKline BV, and IPCRG, all outside the submitted work. K. Schultz received lecture fees from Boehringer, AstraZeneca, Berlin Chemie, Novartis, Chiesi, Mundipharma, Takeda, GSK and MSD, all outside the submitted work. T. van der Molen reports personal reimbursements from GSK, TEVA, Astra Zeneca, Boehringer Ingelheim and study grants from Astra Zeneca and GSK. After this study was terminated, he became employee of GSK. None of these stated conflicts of interest are linked to the current manuscript. T. van der Molen developed the CCQ and holds the copyright.

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Figures

Fig. 1
Fig. 1
Consort flow-chart of the number of patients during follow-up
Fig. 2
Fig. 2
Correspondence between the five- and 15-point Global Rating of Change scale at 12 months follow-up
Fig. 3
Fig. 3
MCID estimates with for dependency adjusted confidence intervals for CAT and CCQ total score. Data are presented as MCID estimates (squares) and their respective confidence interval (horizontal line) adjusted for the dependency of the data. The red vertical lines represents the MCID estimates for CAT and CCQ total score obtained from the literature. Negative values represent improvement in health status
Fig. 4
Fig. 4
MCID estimates with for dependency adjusted confidence intervals for SGRQ total score including standardized estimates for CAT and CCQ total scores. Data are presented as MCID estimates (squares) and their respective confidence interval (horizontal line) adjusted for the dependency of the data. The red vertical line represents the MCID estimate for SGRQ total score obtained from the literature. Negative values represent improvement in health status
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