Mirjana Djeric

Glycated hemoglobin A1c as a modern biochemical marker of glucose regulation.

UNLABELLED GLYCATED HEMOGLOBIN STRUCTURE AND SYNTHESIS OF MOLECULE: Glycated hemoglobin A1c, the major fraction of glycated hemoglobin, is formed by irreversible nonenzymatic glycation. Its concentration depends only on the life span of red blood cells and blood glucose levels. CLINICAL SIGNIFICANCE OF GLYCATED HEMOGLOBIN A1c: It is the key parameter for monitoring the regulation of diabetes and for assessing the risk of microvascular complications. It is a diagnostic criterion for diabetes as well. Its concentration reflects the average value of blood glucose over the last two to three months. The estimated average glucose, a new parameter which facilitates the patients self-monitoring of diabetes, can be calculated from its value. METHODS FOR DETERMINING GLYCATED HEMOGLOBIN A1c AND THEIR STANDARDIZATION: Immunoassay and ion-exchange chromatography are commonly used methods for the glycated hemoglobin determination in routine laboratory practice. The advantage of immunoassay is that there is no need for the sample pre-treatment in order to eliminate unstable glycated hemoglobin A1c intermediary forms, and the possibility of false positive results is lower. The current program of standardization requires traceability to the International Federation of Clinical Chemistry and Laboratory Medicine reference method. REPORTING AND INTERPRETATION OF RESULTS OF GLYCATED HEMOGLOBIN A1c DETERMINATION: Glycated Hemoglobin A1c can be reported as % or as mmol/mol. In our country, it is recommended to use the International Federation of Clinical Chemistry and Laboratory Medicine units (mmol/mol). When interpreting the results, the potential causes of falsely high or low values must always be taken into consideration. RECOMMENDATIONS FOR CLINICAL PRACTICE Periodic determinations of glycated hemoglobin A1c are recommended for monitoring of diabetes regulation. Additionally, the determination is recommended for the diagnosis of diabetes. The target value for the prevention of microvascular complications is < 7% and the diagnostic criterion for diabetes is 6.5%.

The role of holotranscobalamin in examination of vitamin B12 status

INTRODUCTION Holotranscobalamin contains biologically available cobalamin because only holotranscobalamin promotes the uptake of the cobalamin therein by all cells, via specific receptors. Therefore holotranscobalamin has been proposed as a potentially useful alternative indicator of vitamin B12 status. The aim of the present study was to assess usefulness of holotranscobalamin in the evaluation of vitamin B12 status. MATERIAL AND METHODS We examined serum level of holotranscobalamin in 135 subjects divided in four groups according to the serum concentration of vitamin B12: 30 subjects with vitamin B12 <154 pmol/l, 50 subjects with vitamin B12 154-250, 30 subjects with vitamin B12 2251-350 pmol/l, 25 subjects with vitamin B12 >350 pmol/l. RESULTS The results show that in subjects with low vitamin B12 serum level there are those with normal holotranscobalamin concentration (60%) and that in subjects with normal vitamin B12 there are those with low holotranscobalamin concentration (22%). The obtained results also show positive significant correlation between levels of holotranscobalamin and vitamin B12 (r = 0.62, p < -0.001). CONCLUSION We can conclude that biologically active cobalamin, holotranscobalamin, is a useful tool when examining vitamin B12 status especially in subjects with borderline and low vitamin B12 concentrations. Measurements of the serum holotranscobalamin may be superior to total serum cobalamin.