Research article
Data enhancement for co-morbidity measurement among patients referred for sleep diagnostic testing: an observational study
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* Corresponding author: Brenda R Hemmelgarn brenda.hemmelgarn@albertahealthservices.ca
1 Department of Community Health Sciences, Faculty of Medicine, University of Calgary, Calgary, Canada
2 Department of Medicine, Faculty of Medicine, University of Calgary, Calgary, Canada
BMC Medical Research Methodology 2009, 9:50 doi:10.1186/1471-2288-9-50
Published: 15 July 2009Abstract
Background
Observational outcome studies of patients with obstructive sleep apnea (OSA) require adjustment for co-morbidity to produce valid results. The aim of this study was to evaluate whether the combination of administrative data and self-reported data provided a more complete estimate of co-morbidity among patients referred for sleep diagnostic testing.
Methods
A retrospective observational study of 2149 patients referred for sleep diagnostic testing in Calgary, Canada. Self-reported co-morbidity was obtained with a questionnaire; administrative data and validated algorithms (when available) were also used to define the presence of these co-morbid conditions within a two-year period prior to sleep testing.
Results
Patient self-report of co-morbid conditions had varying levels of agreement with those derived from administrative data, ranging from substantial agreement for diabetes (κ = 0.79) to poor agreement for cardiac arrhythmia (κ = 0.14). The enhanced measure of co-morbidity using either self-report or administrative data had face validity, and provided clinically meaningful trends in the prevalence of co-morbidity among this population.
Conclusion
An enhanced measure of co-morbidity using self-report and administrative data can provide a more complete measure of the co-morbidity among patients with OSA when agreement between the two sources is poor. This methodology will aid in the adjustment of these coexisting conditions in observational studies in this area.