In case blood glucose level is well within control and gives stable results, the test is performed every six months intervals. The long-term or chronic complications of diabetes are those that characteristically occur after years of high blood sugar levels. These are diabetic macrovascular and microvascular diseases. The long term complications correlate well with A1c levels.(Web ref 2).
Wild and Bains (2004) cautioned clinical laboratories and point-of-care testing to be careful of the interferences produced in assays by variant Hbs. The majority arise from point mutations in the , , , or Hb chains. Herman et al (2007) also raised the important question of whether A1c can be used as a diagnostic test for diabetes detection and control in ethnic minorities whose mean A1c concentration vary significantly from whites. In the light of these observations the current project intends to analyse literature particularly on blood glucose tests, long term complications of high blood sugar and applicability of HbA1c test to ethnic diabetics.
Studies have shown that glycohaemoglobin values in the "better ranges" correlate with less incidences of diabetic complications later in life (Table 1; Fig 1 b). Type 1 diabetics will typically have hemoglobin A1c levels determined every 3 to 4 months, while Type 2 diabetics will require measurements less often (Web ref 3; Web ref 1). It so because Red blood cells are replaced in about 90 days thus test gives blood glucose levels for that period. Normal blood glucose levels are below 6 percent HbA1c however these vary laboratory to laboratory (McCool and Woodruff 1999; Web ref 1) HbA1c levels compare well with blood glucose levels as shown below:
Table 1. Comparison of HbA1c test and Blood glucose levels (from McCool and Woodruff 1999)
Level of control
Blood glucose (mg/dl)
The rapid fluctuations in blood glucose that normally occur are smoothed out and the long-term level of glucose is now available to clinicians as a HbA1c test, because glycosylated hemoglobin has been shown to correlate with the integrated average blood consumption of glucose over the preceding six to eight weeks (Nathan 1990). Moreover, No preparation is necessary.
Fig1 b) Controlled and uncontrolled diabetes conditions. (from Web ref 1)
Controlled diabetes, less blood glucose results in less glycosylated haemoglobin
Uncontrolled diabetes, more blood glucose results in high glycosylated haemoglobin
HbA1c is also a reasonably sensitive test for gestational diabetes mellitus (GDM) which occurs in pregnant women. The test when conducted on pregnant women, it could pick up 87.1 cases of GDM successfully. The study gives a good alternative to OGTT (oral glucose tolerance test) which is inconvenient and requires fasting (Aldasouqi et al, 2008). The HbA1c test earlier done in laboratories only is now available in relatively economical home version as well (Web ref 4). The control of HbA1c and avoiding long term diabetic complications are discussed later.
Diabetes: An overview
The word 'diabetes'