Abstract
Background/Aims The HMORN includes research centers that are part of integrated delivery systems where the clinical practice and insurance entities are independent (e.g., Geisinger, Marshfield) and where the primary care practice offers the larger population sample. Population denominators in these systems can be defined from insurance membership only, the primary care practice only (i.e., using electronic health records or EHR), or the overlap of the two (i.e., primary care patients may not be members of the insurance entity and visa versa). Methods for defining denominators and person-time for members of an insurance plan are well established. However, such methods have not been developed or validated for primary care practices using the EHR. The aim of this study was to use EHR data from a large primary care practice to derive measures of disease prevalence and incidence and to evaluate the validity of these measures using insurance claims data.
Methods We presented methods for defining population denominators from the EHR at HMORN 2010. One method performed better than others when validating against insurance enrollment. The current study will compare prevalence and incidence of hypertension and diabetes when using the various EHR denominator methods and validate them against incidence and prevalence as calculated from insurance claims. Results will be stratified by age and gender. Disease status will be defined by identifying subjects that had 2 or more outpatient office visits with a diagnosis or with the diagnosis appearing on the problem list. Ninety-five percent confidence intervals will be used to identify statistical differences.
Results A total of 164,030 patients have been identified for inclusion in the analysis. Analysis is ongoing and final results will be presented at HMORN 2011.
Conclusions The choice of denominator method may lead to differences in incidence and prevalence rates. More research is needed to determine which numerator and denominator methods most strongly agree with measures of disease frequency calculated from insurance enrollment and claims.
