Abstract
Objective
To assess the construct validity of the Self-Administered Comorbidity Questionnaire
(SCQ) in patients with systemic sclerosis (SSc) and systemic lupus erythematosus (SLE).
Methods
The SCQ was modified for the SSc cohort to emphasize the objective of recording problems
other than the patients' scleroderma. It was administered to 406 SSc and 147 SLE patients. Construct
validity of the SCQ was evaluated separately in the SSc and SLE cohorts by testing
the hypotheses that a valid comorbidity index should correlate with age and health-related
quality of life (Medical Outcomes Trust Short Form 36 [SF 36]) but not with disease-specific
variables.
Results
The SCQ score correlated with age in the SSc patients only (Tau B=0.37, P<0.001) and not in the SLE patients. It correlated with the SF 36 in both SSc and SLE.
However, it also correlated with several disease-related variables. There was significant
overlap between reports of comorbidities and disease-related problems in the SSc cohort.
Conclusion
Patients with systemic autoimmune diseases cannot distinguish true comorbidities from
conditions related to their index disease and, as such, a self-administered comorbidity
questionnaire does not appear useful in these diseases.
Keywords
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Article info
Publication history
Published online: March 17, 2008
Accepted:
August 3,
2007
Identification
Copyright
© 2008 Elsevier Inc. Published by Elsevier Inc. All rights reserved.