Authors' objectives:

While testing for glycemic control and urine albumin are widely recommended for persons with Types 1 and 2 diabetes mellitus, there has not been a systematic assembly of the literature to assess the risk relation between tests assessing long-term glycemic control or tests assessing the presence of microalbuminuria to future cardiovascular, peripheral vascular, renal, and neurological outcomes (all of which represent end-organ effects of long-term diabetes). This report, commissioned by the American Association of Clinical Chemistry, systematically reviews the literature identifying the risk relation between testing for glycemic control and urine albumin with these important clinical outcomes.

Authors' results and conclusions: The evidence supports a strong, graded relation between the level of glycated hemoglobin and the risk of two major microvascular complications of type 1 and type 2 diabetes, retinopathy and nephropathy. These patterns are observed for various measures of glycated hemoglobin (i.e., HbA1c, HbA1, and total GHb). Cohort studies evaluating coronary artery disease and peripheral arterial disease demonstrated a positive association with glycated hemoglobin exposure in persons with types 1 and 2 diabetes (although risk estimates were much smaller compared to the risk estimates for the microvascular complications). The risk relationship between cerebrovascular disease and glycated hemoglobin is less clear. For studies on urine albumin, reporting of methods for measurement of urine albumin and reporting of cutoffs for microalbuminuria were varied. The evidence supports the association of microalbuminuria at baseline with progression of kidney disease, all-cause death, and cardiovascular morbidity and mortality. These relations appear to be graded with greater levels of urine albumin excretion at baseline predicting greater risk of these outcomes at follow up.

Authors' recommendations: Glycated hemoglobin was strongly associated with an increased risk of microvascular complications as well as macrovascular complications, although the association was weaker for macrovascular disease. Microalbuminuria was associated with progression of chronic kidney disease and the development of cardiovascular morbidity, cardiovascular mortality, and all-cause death. This synthesis is limited by the significant heterogeneity in the measurements of glycated hemoglobin and microalbuminuria as well as heterogeneous measurements for clinical outcomes making comparisons across studies difficult. For research on glycemic control, future work should focus on studying the relation between glycated hemoglobin exposure and the risk of neuropathy and macrovascular complications and determining whether there is a threshold for the effect of glycated hemoglobin on these outcomes. Because of the heterogeneity in the literature on reporting of glycated hemoglobin, future cohort studies and clinical trials should aim to use standardized methods to allow risk comparison across studies. For research on urine albumin, future work should seek to define the optimal and most feasible measures of microalbuminuria and to standardize measurement of microalbuminuria in persons with diabetes. Future research should also characterize the nature of the relation between microalbuminuria and outcomes.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.ahrq.gov/clinic/epcsums/glycasum.htm

Year Published: 2003

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: Agency for Healthcare Research and Quality

Contact Address: Center for Outcomes and Evidence Technology Assessment Program, 540 Gaither Road, Rockville, MD 20850, USA. Tel: +1 301 427 1610; Fax: +1 301 427 1639;

Contact Name: martin.erlichman@ahrq.hhs.gov

Contact Email: martin.erlichman@ahrq.hhs.gov

Copyright: Agency for Healthcare Research and Quality (AHRQ)