Abstract
ObjectivesThe 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.MethodsSubjects 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.ResultsA 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.ConclusionThis 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”.
Highlights
Sarcopenia, often described as the age-related loss of muscle mass and strength, and defined by the European Working Group on Sarcopenia in Older People (EWGSOP2) as “a progressive and generalised skeletal muscle disorder that is associated with increased likelihood of adverse outcomes including falls, fractures, physical disability and mortality”, has been the subject of increased scientific attention as its prevalence and consequences have become more known [1]
This study shows that, for individual subjects, a change in overall quality of life of at least 7.35 points would have to be observed to confirm that a true change, beyond measurement error, has occurred
It demonstrated that the Sarcopenia Quality of Life (SarQoL) questionnaire is a precise instrument, with the observed scores within less than 3 points of the theoretical “true score”
Summary
Sarcopenia, often described as the age-related loss of muscle mass and strength, and defined by the European Working Group on Sarcopenia in Older People (EWGSOP2) as “a progressive and generalised skeletal muscle disorder that is associated with increased likelihood of adverse outcomes including falls, fractures, physical disability and mortality”, has been the subject of increased scientific attention as its prevalence and consequences have become more known [1]. Sarcopenia is confirmed to be present when a patient is diagnosed with low muscle strength and low muscle mass. Projections about the future prevalence of sarcopenia (as diagnosed by the EWGSOP-criteria) in the European Union (EU28) predict a rise from 10.9 million people in 2016 to 18.7 million in 2045 on the low end and from 19.7 million to 32.3 million people on the high end [5]. Sarcopenia is a major public health problem and its impact will continue to grow, which should incite policy makers to act
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