Abstract
BackgroundCombining outcomes and the use of standardized effect measures such as effect size and standardized response mean across instruments allows more comprehensive meta-analyses and should avoid selection bias. However, such analysis ideally requires that the instruments correlate strongly and that the underlying assumption of similar responsiveness is fulfilled. The aim of the study was to assess the correlation between two widely used health-related quality of life instruments for patients with chronic obstructive pulmonary disease and to compare the instruments' responsiveness on a study level.MethodsWe systematically identified all longitudinal studies that used both the Chronic Respiratory Questionnaire (CRQ) and the St. George's Respiratory Questionnaire (SGRQ) through electronic searches of MEDLINE, EMBASE, CENTRAL and PubMed. We assessed the correlation between CRQ (scale 1 – 7) and SGRQ (scale 1 – 100) change scores and compared responsiveness of the two instruments by comparing standardized response means (change scores divided by their standard deviation).ResultsWe identified 15 studies with 23 patient groups. CRQ change scores ranged from -0.19 to 1.87 (median 0.35, IQR 0.14–0.68) and from -16.00 to 3.00 (median -3.00, IQR -4.73–0.25) for SGRQ change scores. The correlation between CRQ and SGRQ change scores was 0.88. Standardized response means of the CRQ (median 0.51, IQR 0.19–0.98) were significantly higher (p < 0.001) than for the SGRQ (median 0.26, IQR -0.03–0.40).ConclusionInvestigators should be cautious about pooling the results from different instruments in meta-analysis even if they appear to measure similar constructs. Despite high correlation in changes scores, responsiveness of instruments may differ substantially and could lead to important between-study heterogeneity and biased meta-analyses.
Highlights
Combining outcomes and the use of standardized effect measures such as effect size and standardized response mean across instruments allows more comprehensive meta-analyses and should avoid selection bias
Investigators often deal with this challenge by standardizing scores from different instruments and combining them as unit-free scores – effect sizes or standardized response means (SRMs)[2,5,6] critics have noted that, because standard deviations (SD) may vary substantially from study to study, treatment effects that are homogeneous when expressed in their original unit can become heterogeneous when expressed as (SRM) [7]
Chronic Respiratory Questionnaire (CRQ) change scores ranged from -0.19 to 1.87 and for the St George's Respiratory Questionnaire (SGRQ) from -16.10 to 3.00
Summary
Combining outcomes and the use of standardized effect measures such as effect size and standardized response mean across instruments allows more comprehensive meta-analyses and should avoid selection bias. Such analysis ideally requires that the instruments correlate strongly and that the underlying assumption of similar responsiveness is fulfilled. Investigators often deal with this challenge by standardizing scores from different instruments and combining them as unit-free scores – effect sizes or standardized response means (SRMs)[2,5,6] critics have noted that, because standard deviations (SD) may vary substantially from study to study, treatment effects that are homogeneous when expressed in their original unit can become heterogeneous when expressed as (SRM) [7]. Investigators could transform CRQ into SGRQ scores or vice versa using transformation coefficients from regression analyses [8]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
