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Standard error of measurement and smallest detectable change of the SarQoL questionnaire: an analysis of subjects from 9 validation studies

Standard error of measurement and smallest detectable change of the SarQoL questionnaire: an analysis of subjects from 9 validation studies
Standard error of measurement and smallest detectable change of the SarQoL questionnaire: an analysis of subjects from 9 validation studies
Objectives

The Sarcopenia Quality of Life (SarQoL) questionnaire, a sarcopenia-specific patient-reported outcome measure, evaluates quality of life with 55 items. It produces 7 domain scores and 1 overall quality of life score, all between 0 and 100 points. This study aims to contribute to the interpretation of the SarQoL scores by calculating the standard error of measurement (SEM) and smallest detectable change (SDC) in a sample of subjects from 9 studies.

Methods

Subjects from 9 studies (conducted in Belgium, Brazil, Czech Republic, England, Greece, Lithuania, Poland and Spain) were included. The SEM, a measure of the error in the scores that is not due to true changes, was calculated by dividing the standard deviation of the difference between test and retest scores (SDdiff) by √2. The SDC, defined as change beyond measurement error, was calculated by multiplying SDdiff by 1.96. Bland-Altman plots were assessed for the presence of systematic errors.

Results

A total of 278 sarcopenic subjects, aged 77.67 ± 7.64 years and 61.5% women, were included. The SEM for the overall SarQoL score ranged from 0.18 to 4.20 points for the individual studies, and was 2.65 points when all subjects were analyzed together. The SDC for the overall score ranged from 0.49 to 11.65 points for the individual studies, and was 7.35 points for all subjects. The Bland-Altman plots revealed no systematic errors in the questionnaire.

Conclusion

This study shows that, for individual subjects, a change in overall quality of life of at least 7.35 points (on a scale from 0 to 100) would have to be observed to confirm that a true change, beyond measurement error, has occurred. It also demonstrated that the SarQoL questionnaire is a precise instrument, with the observed scores within less than 3 points of the theoretical “true score”.
1932-6203
Geerinck, Anton
06bb9a12-8354-4567-814f-743a14a6b881
Alekna, Vidmantas
c4546409-8c3a-45a7-bd87-e1153224bb15
Beaudart, Charlotte
bdc9da98-791a-474b-9745-be0695a4d8a9
Bautmans, Ivan
5c302aed-9ac6-4f70-9c1b-cb96a9f4116b
Cooper, Cyrus
e05f5612-b493-4273-9b71-9e0ce32bdad6
De Souza Orlandi, Fabiana
766ba882-e226-4f8d-89a9-1679dcb78437
Konstantynowicz, Jerzy
1f88631c-ce9e-4384-974d-a886e5290c1f
Montero-Errasquin, Beatriz
7bd56645-a455-4b32-a929-06fa7bc74043
Topinkova, Eva
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Tsekoura, Maria
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Reginster, Jean Yves
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Bruyère, Olivier
ba727e54-ca17-4fa8-be3d-4729fb4b8c0d
Geerinck, Anton
06bb9a12-8354-4567-814f-743a14a6b881
Alekna, Vidmantas
c4546409-8c3a-45a7-bd87-e1153224bb15
Beaudart, Charlotte
bdc9da98-791a-474b-9745-be0695a4d8a9
Bautmans, Ivan
5c302aed-9ac6-4f70-9c1b-cb96a9f4116b
Cooper, Cyrus
e05f5612-b493-4273-9b71-9e0ce32bdad6
De Souza Orlandi, Fabiana
766ba882-e226-4f8d-89a9-1679dcb78437
Konstantynowicz, Jerzy
1f88631c-ce9e-4384-974d-a886e5290c1f
Montero-Errasquin, Beatriz
7bd56645-a455-4b32-a929-06fa7bc74043
Topinkova, Eva
5e0d543d-f071-46df-80dd-a9defc2c961e
Tsekoura, Maria
94d35c78-17c9-4982-b3cb-7efc9857aa8f
Reginster, Jean Yves
33684a35-87f7-4b8d-bb91-4da2b809f855
Bruyère, Olivier
ba727e54-ca17-4fa8-be3d-4729fb4b8c0d

Geerinck, Anton, Alekna, Vidmantas, Beaudart, Charlotte, Bautmans, Ivan, Cooper, Cyrus, De Souza Orlandi, Fabiana, Konstantynowicz, Jerzy, Montero-Errasquin, Beatriz, Topinkova, Eva, Tsekoura, Maria, Reginster, Jean Yves and Bruyère, Olivier (2019) Standard error of measurement and smallest detectable change of the SarQoL questionnaire: an analysis of subjects from 9 validation studies. PLoS ONE, 14 (4), [e0216065]. (doi:10.1371/journal.pone.0216065).

Record type: Article

Abstract

Objectives

The Sarcopenia Quality of Life (SarQoL) questionnaire, a sarcopenia-specific patient-reported outcome measure, evaluates quality of life with 55 items. It produces 7 domain scores and 1 overall quality of life score, all between 0 and 100 points. This study aims to contribute to the interpretation of the SarQoL scores by calculating the standard error of measurement (SEM) and smallest detectable change (SDC) in a sample of subjects from 9 studies.

Methods

Subjects from 9 studies (conducted in Belgium, Brazil, Czech Republic, England, Greece, Lithuania, Poland and Spain) were included. The SEM, a measure of the error in the scores that is not due to true changes, was calculated by dividing the standard deviation of the difference between test and retest scores (SDdiff) by √2. The SDC, defined as change beyond measurement error, was calculated by multiplying SDdiff by 1.96. Bland-Altman plots were assessed for the presence of systematic errors.

Results

A total of 278 sarcopenic subjects, aged 77.67 ± 7.64 years and 61.5% women, were included. The SEM for the overall SarQoL score ranged from 0.18 to 4.20 points for the individual studies, and was 2.65 points when all subjects were analyzed together. The SDC for the overall score ranged from 0.49 to 11.65 points for the individual studies, and was 7.35 points for all subjects. The Bland-Altman plots revealed no systematic errors in the questionnaire.

Conclusion

This study shows that, for individual subjects, a change in overall quality of life of at least 7.35 points (on a scale from 0 to 100) would have to be observed to confirm that a true change, beyond measurement error, has occurred. It also demonstrated that the SarQoL questionnaire is a precise instrument, with the observed scores within less than 3 points of the theoretical “true score”.

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More information

Accepted/In Press date: 12 April 2019
e-pub ahead of print date: 29 April 2019

Identifiers

Local EPrints ID: 430764
URI: http://eprints.soton.ac.uk/id/eprint/430764
ISSN: 1932-6203
PURE UUID: 211962df-2924-43e3-87cd-430bef6b64c7
ORCID for Cyrus Cooper: ORCID iD orcid.org/0000-0003-3510-0709

Catalogue record

Date deposited: 10 May 2019 16:30
Last modified: 26 Nov 2021 02:39

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Contributors

Author: Anton Geerinck
Author: Vidmantas Alekna
Author: Charlotte Beaudart
Author: Ivan Bautmans
Author: Cyrus Cooper ORCID iD
Author: Fabiana De Souza Orlandi
Author: Jerzy Konstantynowicz
Author: Beatriz Montero-Errasquin
Author: Eva Topinkova
Author: Maria Tsekoura
Author: Jean Yves Reginster
Author: Olivier Bruyère

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