Glycated hemoglobin (HbA1c): old dogmas, a new perspective?

UO di Diagnostica Ematochimica, Dipartimento di Patologia e Medicina di Laboratorio, Azienda Ospedaliero-Universitaria di Parma, Parma, Italy.
Clinical Chemistry and Laboratory Medicine (Impact Factor: 3.01). 05/2010; 48(5):609-14. DOI:10.1515/CCLM.2010.144
Source: PubMed

ABSTRACT The hemoglobin A1c (HbA1c) assay provides a reliable measure of chronic glycemia and correlates well with the risk of long-term diabetes complications, so that it is currently considered the test of choice for monitoring and chronic management of diabetes. Recently, HbA1c testing has been included within the diagnostic criteria recommended for diagnosis of diabetes in nonpregnant individuals by the American Diabetes Association (ADA). The emerging concept that HbA1c can be used rather than blood glucose in the diagnosis of diabetes is highly appealing for a variety of reasons, including less sensitivity to preanalytical variables, lower within subject biological variability, little to null interference from diurnal variations, acute stress and common drugs which are known to influence glucose metabolism, as well as the fact that one single measurement might provide information for both diagnosing diabetes and tracking glycemic control. On the other hand, the use of HbA1c for screening and diagnosing diabetes also carries some limitations, including the worse diagnostic performance in different populations (i.e., pregnancy, elderly and non-Hispanic blacks), the risk of overdiagnosis in subjects with iron deficiency anemia, in subjects genetically predisposed to hyperglycation, and in those with increased red blood cell turnover. There is also a higher risk of misdiagnosis in patients with end-stage renal disease and heavy alcohol consumption. Finally, HbA1c testing might be biased due to the interference from several hemoglobin variants, is characterized by a higher imprecision than blood glucose measurement, and is more expensive. This paper will critically summarize the potential advantages and limitations of HbA1c as a recommended test for diagnosing diabetes.

0 0
  • Source
    Clinical Chemistry and Laboratory Medicine 02/2012; 50(2):189-90. · 3.01 Impact Factor
  • Source
    [show abstract] [hide abstract]
    ABSTRACT: To determine the glycosylated haemoglobin (HbA(1c)) cut-points for diabetes and impaired fasting glucose (IFG) among Asian Indians. Participants (n=525) were a random sample selected from the India Health Study. Based on history and fasting plasma glucose (FPG), participants were classified into known diabetes, newly diagnosed diabetes (NDD), impaired fasting glucose (IFG) [ADA and WHO criteria] or normal fasting glucose (NFG). Receiver Operating Characteristic curves were used to identify the optimum sensitivity and specificity for defining HbA(1c) cut-points for NDD and IFG against the FPG criteria. There were 64 participants with a known history of diabetes. Of the remaining 461, IFG was present in 44.7% (ADA) and 18.2% (WHO), and 10.4% were NDD. Mean HbA(1c) were 5.4 (±0.04)% for NFG; 5.7 (±0.06)% among IFG-ADA, 5.8 (±0.09)% among IFG-WHO; 7.5 (±0.33)% for NDD and 8.4 (±0.32)% for known diabetes. Optimal HbA(1c) cut-point for NDD was 5.8% (sensitivity=75%, specificity=75.5%, AUC=0.819). Cut-point for IFG (ADA) was 5.5% (sensitivity=59.7%, specificity=59.9%, AUC=0.628) and for IFG (WHO) was 5.6% (sensitivity=60.7%, specificity=65.1%, AUC=0.671). In this study population from north and south regions of India, the HbA(1c) cut-point that defines NDD (≥5.8%) was much lower than that proposed by an international expert committee and the American Diabetes Association (≥6.5%). A cut-point of ≥5.5% or ≥5.6% defined IFG, and was slightly lower than the ≥5.7% for high risk proposed, but accuracy was less than 70%.
    Primary care diabetes. 07/2011; 5(2):95-102.
  • [show abstract] [hide abstract]
    ABSTRACT: BACKGROUND: In 2010 Singapore's National Health Survey reported 11.3% of the population between 18-69years of age with diabetes, compared to 8.2% in 2006. This increasing trend reinforces the dependence on HbA1c for management of glycemic control. METHODS: To determine the incidence of hemoglobin variants received from our diabetic population who are attending the National University Hospital for testing of their HbA1c and determined whether the hemoglobin variant caused an interpretation issue. We reviewed all chromatograms from patients sending a sample for HbA1c analysis for a three month period. Analysis was performed on the Variant II using the HbA2/HbA1c Dual program. RESULTS: Our sub analysis identified 2 cases of α thalassemia, 2 cases of β thalassemia; 5 cases of Hemoglobin E variant homozygous 1 case of Hemoglobin J variant; 110 cases of Hemoglobin E, 7 cases of Hemoglobin S, 1 case of Hemoglobin C and 1 case of Hemoglobin D, all heterozygous. HbA1c results could be confidently reported in all cases except the homozygote variant and the Hemoglobin J variant. CONCLUSIONS: Overall we obtained a prevalence of 2.3% of hemoglobin variants in our diabetic population being screened by HbA1c using Variant II.
    Clinica chimica acta; international journal of clinical chemistry 10/2012; · 2.54 Impact Factor