Linking clinical relevance and statistical significance in evaluating intra-individual changes in health-related quality of life.
OBJECTIVE
To compare the standard error of measurement (SEM) with established standards for clinically relevant intra-individual change in an evaluation of health-related quality of life.


METHODS
Secondary analysis of data from a randomized controlled trial.


METHODS
Six hundred and five outpatients with a history of cardiac problems attending the general medicine clinics of a major academic medical center.


METHODS
Baseline and follow-up interviews included a modified version of the Chronic Heart Failure Questionnaire (CHQ) and the SF-36. The SEM values corresponding to established standards for minimal clinically important differences (MCIDs) on the CHQ were determined. Individual change on the SF-36 was explored using the same SEM criterion.


RESULTS
One-SEM changes in this population corresponded well to the patient-driven MCID standards on all CHQ dimensions (weighted kappas (0.87; P < 0.001). The distributions of outpatients who improved, remained stable, or declined (defined by the one-SEM criterion) were generally consistent between CHQ dimensions and SF-36 subscales.


CONCLUSIONS
The use of the SEM to evaluate individual patient change should be explored among other health-related quality of life instruments with established standards for clinically relevant differences. Only then can it be determined whether the one-SEM criterion can be consistently applied as a proxy for clinically meaningful change.
Wyrwich
K W
KW
Saint Louis University School of Public Health, MO 63108-3342, USA. wyrwichk@slu.edu
Nienaber
N A
NA
Tierney
W M
WM
Wolinsky
F D
FD
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D015982:Bias; D002908:Chronic Disease; D003327:Coronary Disease / Q000453:epidemiology; D005260:Female; D006305:Health Status Indicators; D006333:Heart Failure / Q000453:epidemiology; D006801:Humans; D007407:Interviews as Topic / Q000379:methods; D008173:Lung Diseases, Obstructive / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D011795:Surveys and Questionnaires