Glycated hemoglobin

, Also referred to as HbA1c glycated hemoglobin ( GHb ), is red blood pigment (hemoglobin ) which is bound to glucose ( glycation ). The coupling of glucose to hemoglobin takes place without enzymes ( Amadori rearrangement), therefore it is not to glycosylation.

The proportion of HbA1c in the total hemoglobin is detected in blood tests. It provides information on the blood sugar levels of the last eight weeks ( mean age of erythrocytes ) and is therefore also referred to as long-term blood sugar or blood sugar memory.

Units

Since it is not a specific reaction that produces various Glykierungsprodukte. To standardize the measurement world, a working group of the IFCC (International Federation of Clinical Chemistry and Laboratory Medicine ), the HbA1c is defined as the stable product of a coupling of glucose to the N -terminal valine of the beta chain of hemoglobin. The conceived in the unit was leaking %.

The introduced as recommended by IFCC, international unit is mmol / mol hemoglobin and corresponds to the per mille.

Under the directive of the German Medical Association on 1 April 2008, the HbA1c value is now (also) specified in this unit. To better distinguish the % value, this value is also referred to as HbA1cM. The conversion formula is:

HbA1c (mmol / mol Hb) = (HbA1c [% ] - 2.15 ) x 10.929

Sample collection ( pre-analysis )

The HbA1c is determined from whole blood, which usually contains EDTA as an anticoagulant. Requirements for the storage and treatment of the sample material depend on the analysis system used. Usually the sample is one to two weeks stored at 4 ° C or can be stored for several months at -20 ° C.

Laboratory diagnostics

For the measurement of the value of laboratory machines are mainly used today, which conduct a photometric measurement process fully automatically in microtiter plates. The modern instruments today use monochromatic light-emitting diodes in place of ( broadband ) halogen lamps. LEDs have the advantage that hardly any heat in the device and thus no cooling of the machine is necessary. Thus, you can work with less reagent and sample volume - which represents a significant cost advantage for the user.

When measuring principle is an enzyme immunoassay is used. This method of measurement leads with single measurements make significant difference, by measuring several identical samples in microtiter plates can be personalized with computational methods, however, identify sufficiently reliable averages.

Normal range and interpretation

The normal range is 29-42 mmol / mol Hb or 4-6 per cent.

False high HbA1c is measured in iron deficiency anemia, since in this case the degradation of erythrocytes is slowed.

False low values ​​may occur in hemolytic anemia, liver cirrhosis, thalassemia, chronic renal failure and increased de novo synthesis of erythrocytes. The values ​​may be biased even after a greater blood loss or blood transfusion.

Diabetes mellitus

A lying within the normal range HbA1c includes diabetes mellitus is not enough. However, values ​​above 6% support a suspected diagnosis.

The HbA1c is measured in patients with diabetes mellitus every three months. The goal of therapy is that the HbA1c remains below 7-8 % in order to delay possible long-term consequences of this condition as long as possible or avoid.

In individual cases, the determination despite NGSP standardization still show strong method-dependent differences. It is therefore recommended to monitor a patient always with the same method.

Conversion table

The following table shows the conversion of HbA1c in the average blood sugar levels. The figures in the table should serve only as a rough guide, since short-term high values ​​(eg after meals) partially received no stable bonds ( raise the average HbA1c not ).

For the conversion of the average blood glucose level in HbA1c following formulas are used:

• HbA1c [% ] = (mean blood glucose [mg / dl ] 86 ) / 33.3
• HbA1c [% ] = ( Mean blood sugar (plasma) [mg / dl ] 77.3 ) / 35.6