The effects of complications and comorbidities on the quality of preventive diabetes care: a literature review

Although concurrent conditions such as complications and comorbidities are common in people with diabetes, both are often omitted from studies of the quality of diabetes preventive care. This systematic review of the literature on the quality of diabetes preventive care assesses not only trends in the reporting of and adjusting for complications and comorbidities, but also the limitations of current measures of complications and comorbidities. This review identified 34 studies in which the quality of diabetes preventive care was assessed with process measures and complications or comorbidities were reported. More often than not, the studies identified the presence of certain complications or comorbidities, counted complications or comorbidities, or used comorbidity indices to measure morbidity. While earlier studies reported the prevalence of complications or comorbidities, more recent studies use complications or comorbidities as covariates in regression models. Despite this progress, the effects of complications and comorbidities on care processes are unclear because of cross-study variation among measures of complications and comorbidities and because very few studies address the independent effects of complications and comorbidities. Effective measures of complications and comorbidity are necessary to evaluate the quality of diabetes preventive care, particularly for patients with concurrent conditions. Current reported measures of complications and comorbidities may not address constructs related to quality, underscoring the need for a methodology that is better than the approaches now documented in the literature.