International journal of epidemiology
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Review
Use of comorbidity scores for control of confounding in studies using administrative databases.
Comorbidity scores are increasingly used to reduce potential confounding in epidemiological research. Our objective was to compare metrical and practical properties of published comorbidity scores for use in epidemiological research with administrative databases. ⋯ Comorbidity scores, particularly the CDS or D'Hoore's CI based on three-digit ICD-9 codes, may be useful in exploratory data analysis. However, residual confounding by comorbidity is inevitable, given how these scores are derived. How much residual confounding usually remains is something that future studies of comorbidity scores should examine. In any given study, better control for confounding can be achieved by deriving study-specific weights, to aggregate comorbidities into groups with similar relative risks of the outcomes of interest.
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Surveillance of infectious diseases is done in many countries. The aims of such surveillance include the detection of epidemics. In the present study, the possibility of detecting an epidemic in its early stage using a simple method was evaluated for 16 infectious diseases. ⋯ The early stage of epidemics of some infectious diseases might be detectable using this simple method.