A Full-Automated Analyzer for HbA1C using Newly Developed Stationary Phase

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In diabetics, the concentration of HbA1C gives valuable information on the regulation of carbohydrate metabolism during a period of 8 to 12 weeks before its determination, and it has recently come to be recognized as a useful parameter in the management of patients with diabetes mellitus. Of the various methods developed for estimating HbA1C, the one most frequently cited is that of Trivelli and her co-workers. It is, however, a time-consuming method, and in addition, very complicated technology. High-performance liquid chromatography, that is, HPLC, has also been used in the assay of glycosylated hemoglobin. This technique is not as time-consuming, and is more precise. Furthermore, it requires only a minute amount of blood. However, the ion exchange resin usually used in this sytem, Bio Rex 70, is too soft to bear repeated loads of high pressure. Gel deformation may occur, resulting in the clogging of the column and failure to sustain a constant flow. Inaccurate data is produced after the column has been used many times. Recently, we synthesized a new type of hydrophobic stationary phase to be used for this kind of HPLC assay. This stationary phase, Micropearl SFWA1C, is composed of crosslinked synthetic organic polymers and the separation mechanism is based upon mixed interaction which are reversed phase partition chromatography and ion-exchange chromatography. The polymers are hard enough to withstand repeated used and are able to make a better separation of minor component of hemoglobin in a shorter elution time compared to the convetional method. The HgA1C values obtained by this column are correlated well with those of obtained by Bio Rex 70 column. Employing this Micropearl SFWA1C column, the HbA1C automated analyzer has developed. It is operated by a microcomputer control which includes an alarm system with self-checking of pressure, flow volume, and data processing. It has a snake-chain type auto-sampler which carries cups of the samples. The system employs bichromatic measurements (one at 415nm and one at 500nm), using the difference in the two measurements to eliminate error introduced by variations in the light source. In this system, only 3μl of whole blood is required as the specimen. The specimen is added to 450μl of the hemolytic reagent, which is an aqueous solution of sodium azide. The resultant sample can be injected directly into the injection valve. As for the precision data of this method, the coefficient of variation of the intraassays for normal subjects was 3.23%, and 3.38% for diabetic subjects. The coefficient of variation of the interassays for normal subjects was 3.85%, and 3.90% for the diabetics. Next, from the histogram of HbA1C in normal Japanese subjects, we calculated the normal range of this hemoglobin component as the mean, 4.83±0.94%, which is twice the standard deviation. The correlation between the values for present HbA1C levels and fasting blood sugar levels measured at various times, the best correlation was found for the blood sugar level measured two months before the sample for the HbA1C assay was taken. Good correlation was found for values from one month before, and fair correlation for three months before. HbA1C values correlated least well when compared with values for FBS measured on the same day. As mentioned above, this method has the merits of a simple procedure and a column which can be used repeatedly, and should prove itself useful in a wide variety of clinical situations.
Japan Society of Clinical Chemistryの論文

A Full-Automated Analyzer for HbA<SUB>1</SUB>C using Newly Developed Stationary Phase

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