HbA1c as the Diagnostic Test for Diabetes?

Back in June 2009 an international committee recommended that the hemoglobin A1c – also known as glycated hemoglobin – should become the standard test for diagnosing diabetes.  For instance, type 2 diabetes should be diagnosed in anyone with an HbA1c of 6.5% or greater, without any glucose testing (except in those patients where hbA1c might be inappropriate – see below).  A review of this proposal, giving a number of pros and cons, is published in the British Medical Journal.

The advantages of HbA1c include:

Only a single, non-fasting blood sample required (instead of the fasting, 2-hr and maybe 1-hr samples for blood glucose).

Very small day-to-day variability

Gives an overlook ‘view’ of glucose in the blood during the previous weeks or even months.

Already the most common way to guide the management of diabetes.

Disadvantages of using HbA1c for diagnosis include:

The presence of any abnormal hemoglobin – e.g. sickle cell disease or hemoglobin C, found in 10% of African Americans - affects the measurement HbA1c.

Iron-deficiency anemia causes a 1-1.5% rise in HbA1c readings.

HbA1c appears 1% lower in patients taking antiretroviral drugs (i.e. HIV subjects).

Effects of aging and ethnicity – HbA1c is 0.4% higher in70-year-olds (vs. 40-year-olds) and Afro-Caribbeans.

Standardized testing is not yet universally acceptable – values of a standard 6.5% serum ranged from5.8% to 7.4% in tests done at 250 UK labs.

The authors of this analysis make a plea for further consideration and experience with HbA1c testing before a determined switch to the test as the specific diagnostic tool for diabetes.      

As an additional example of the continued usefulness of blood sugar sampling, I mention a new report that a 1-hour post-meal glucose level of 155 mg/dL or greater is a marker for increased cardiovascular risk.  It will take years for this sort of evidence to be gathered for HbA1c testing.

Comments

[harliallimb]

Weight loss is a reduction of body weight that is triggered by exercise, dieting or an involuntary condition such as an illness. As it is well known when the body does not get enough calories it starts to burn the fat that was deposited in the fat tissue. Normal intake of calories for a human being is about 1800-2200 calories a day. One gram of burned fat produces 9 calories so it is easy to count how much fat are you burning when you lower your calories intake.

Dieting or voluntary weight loss nowadays is very common for people with health problems like obesity, heart dysfunction or for people who might not necessarily need it but want to look good. Weight loss or even fast weight loss may be caused by illness that are associated with such severe conditions like:

* Cancer
* Chronic diarrhea
* Chronic inflammation

Obesity is a condition of extreme overweight when the body mass index or BMI is above 30. Or for people with over risk factors as hypertension or diabetes above 27. The weight loss drugs used for fighting obesity is most commonly given only by prescription and should not be used without doctors supravision. Most of the weight loss drugs work by suppressing the appetite only a few like Xenical have different therapeutic action.

[kumar]

It can also be important to know, how abnormal HbA1C effect O2 concentration by decreased performance due to glycated hemoglobin. Does abnormal HbA1C cause decreased performance of hemoglobin or decreased O2 concentration?

[Robert Griffith]

Kumar:
I think the short answer to your comment is 'yes'. A recent study shows that erythrocytes in diabetics (diagnosed by HbA1c levels) behave differently with regard to ATP-stimulated O2 changes than in normals. Not a direct correlation, but suggestive. In an older study, nitric oxide-haemoglobin binding was increased in patients with Type I diabetes; thus correlated with the HbA1c concentration. An altered metabolic fate of nitric oxide would probably influence microvascular regulation and tissue perfusion - something seen in diabetic vascualr changes.
The 2 studies are at:
http://ajpheart.physiology.org/cgi/content/abstract/299/2/H566
http://www.springerlink.com/content/9rfmrjbelhbdutye/
I hope this helps - as you will realize, I'm out of my depth when it comes to cellular physiology.
Bob G.

[kumar]

Hi Robert,

Thanks for reply & link. Many time when I visit some remote pollution & stress free area, I noticed that my glucose levels improve. So a better understanding on O2 levels related to HbA1C & diabetes can help. Regards.