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Clinical Chemistry 49: 269-274, 2003; 10.1373/49.2.269
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(Clinical Chemistry. 2003;49:269-274.)
© 2003 American Association for Clinical Chemistry, Inc.

New Enzymatic Assay for Glycohemoglobin

Ikunosuke Sakurabayashi1, Tatsurou Watano1, Satoshi Yonehara2a, Kaori Ishimaru2, Kaoru Hirai2, Tsuguki Komori2 and Masayuki Yagi2

1 Department of Clinical Pathology, Jichi Medical School Omiya Medical Center, 1-847 Amanuma-cho, Saitama-shi, Saitama-ken, Japan 330-8503.

2 ARKRAY, Inc., 57 Nishi Aketa-Cho, Higashi-Kujo Minami-Ku, Kyoto, Japan 601-8045.

aAuthor for correspondence. Fax 81-75-661-9435; e-mail yonehara{at}arkray.co.jp.


   Abstract
Top
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 References
 
Background: Previous methods to measure glycohemoglobin (GHb) have been time-consuming or imprecise; we therefore developed a new enzymatic assay for GHb.

Methods: Blood cells were first hemolyzed, and hemoglobin was digested with protease to yield fructosyl amino acid. Fructosyl amino acid oxidase acts on the fructosyl amino acid and generates hydrogen peroxide, which reacts with chromogens in the presence of peroxidase. Total hemoglobin was measured spectrometrically in the same reaction tube. The results were reported as the ratio of the concentrations of GHb and hemoglobin.

Results: The measured values were comparable to those determined with a HPLC method and with an immunoassay in blood samples from 2854 patients with diabetes. Regression analysis for the enzymatic assay (y) vs the HPLC method (x) produced the following: r = 0.979; slope, 0.994 [95% confidence interval (CI), 0.986–1.001]; y-intercept, 0.04% (95% CI, -0.09% to 0.01%); n = 2854. For the enzymatic assay (y) vs the immunoassay (x), the regression statistics were as follows: r = 0.982; slope, 1.002 (95% CI, 0.995–1.009); y-intercept, 0% (95% CI, -0.05% to 0.05%); n = 2854.

Conclusions: The values measured by the new enzymatic assay are sufficiently correlated with those of the conventional HPLC method and immunoassay, but the proposed assay for GHb is rapid and has high precision.


   Introduction
Top
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 References
 
Glycohemoglobin (GHb)1 is an important marker in the diagnosis and treatment of diabetes mellitus (1)(2)(3)(4). Recently, the significance of hemoglobin A1c (HbA1c) was further clarified by the report of the Diabetes Control and Complications Trial (5)(6). HbA1c is mostly measured by HPLC and immunoassay.

The HPLC method can detect abnormal Hb with favorable reproducibility and a CV <1% (7)(8)(9)(10). However, a large dedicated device and a long run time are required. The HPLC method requires ~4 h to analyze 100 samples. In a laboratory measuring thousands of samples, dozens of HPLC devices are necessary. In addition, many personnel are needed to maintain the instrumentation.

The immunoassay can be adapted to an automated analyzer, and a large number of samples can be measured in a short time. However, with this method, the total Hb and the GHb need to be measured separately (11)(12)(13). Moreover, the reproducibility is not good (CV, 3–5%), and the calibration curve is unstable and cannot be held for 24 h. Therefore, researchers and clinicians await a method that could solve these problems.

We describe a new enzymatic assay for measuring GHb in which Hb in the sample is digested with a specific protease to generate fructosyl amino acid (Fig. 1 ).



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  		Figure 1. Principle of the enzymatic assay for GHb.

The specimen can be whole blood or blood cells. Erythrocytes are hemolyzed by Reagent 1. Hb is digested with a specific protease in Reagent 2, and fructosyl amino acid is generated. Total Hb is measured by absorbance at an optional wavelength from 500 to 670 nm in ~4 min. FAOD in Reagent 3 reacts on this fructosyl amino acid and generates H2O2, which reacts with DA-64 via POD; the DA-64 is then converted to Bindschedler’s green. GHb is measured by absorbance at an optional wavelength from 660 to 760 nm in ~8 min.

Fructosyl amino acid reacts in the presence of fructosyl amino acid oxidase (FAOD) to generate H2O2, the concentration of which is proportional to that of GHb in the blood. Peroxidase (POD) catalyzes the reaction of H2O2 and chromogen to develop color, which is proportional to the concentration of GHb in the sample. The total Hb concentration is obtained by measuring the color produced by Hb digested with the specific protease. The final result is reported as the concentration ratio of GHb to Hb.


   Materials and Methods
Top
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 References
 
materials
Specimens were collected in potassium EDTA sample tubes (VENOJECT II DK; 2 mL; Terumo Corp.) from patients of the Omiya Medical Center, Jichi Medical School. Specimens for measurement were blood cells that were obtained from the collected specimens by centrifugation (RL-101 centrifuge and rotor TS-7; Tomy Seiko) at 1500g for 15 min. The specimens were chosen at random, so that they could not be linked with a specific patient. Five samples with similar GHb values were collected from patients and from healthy persons and were mixed together to prepare the pooled sample.

reagents for the enzymatic assay
Three measurement reagents were used. Reagent 1 was composed of 80 mmol/L N-cyclohexyl-2-aminoethanesulfonic acid (Dojindo), 30 mmol/L MOPS (Dojindo), and 9 g/L polyoxyethylene lauryl ether (Nihon Surfactant Kogyo K. K.). Reagent 2 was composed of 4000 kU/L metalloproteinase (ARKRAY, Inc.); 2 mmol/L 2-(iodophenyl)-3-(2,4-dinitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium, monosodium salt (WST-3, Dojindo); 3 mmol/L MES (Dojindo); and 5 mmol/L CaCl2. The metalloproteinase is a specific protease that has an optimum pH at 7.0–8.0 and is activated by Ca2+. Reagent 3 was composed of 26 kU/L FAOD (ARKRAY) (14)(15)(16); 78 kU/L POD (Kikkoman); 0.08 mmol/L N-(carboxymethylaminocarbonyl)-4,4'-bis(dimethylamine)-diphenylamine, sodium salt (DA-64; Wako Pure Chemical Industries, Ltd.); and 300 mmol/L Tris-HCl.

enzymatic assay
To hemolyze the sample, we mixed 0.3 mL of Reagent 1 and 0.01 mL of blood cells in a 1.5-mL microtube. The sample was measured with an automated analyzer (JCA-BM12; JEOL Ltd.; Fig. 2 ). The Hb was resolved by the specific protease, and fructosyl amino acid was separated from Hb in 3–5 min. The total Hb concentration was measured by absorbance at an optional wavelength from 500 to 670 nm for ~5 min. FAOD produced H2O2 from fructosyl amino acid. H2O2 then reacted with DA-64 via POD, and the DA-64 was converted to Bindschedler’s green, which has an absorbance maximum at 727 nm. The GHb concentration was determined by measuring the absorbance of Bindschedler’s green at optional wavelength from 660 to 760 nm for ~8 min.



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  		Figure 2. Schematic of the enzymatic assay performed on the JCA-BM12 analyzer.

Blood cells are hemolyzed by Reagent 1. The Hb is resolved by the specific protease, and fructosyl amino acid is separated from Hb in 3–5 min. The total Hb concentration is measured by absorbance at optional wavelength from 500 to 670 nm in ~5 min. FAOD produces H2O2 from the fructosyl amino acid. H2O2 reacts with DA-64 via POD; the DA-64 is then converted to Bindschedler’s green. The GHb concentration is measured from the Bindschedler’s green at an optional wavelength from 660 to 760 nm in ~8 min.

Calibration was performed with use of a calibrator before the first run every day. The calibration formula was a polygonal line. The calibrator measured zero, low, and high values; the GHb value; and the Hb value, which were based on values of standard material established by the Japanese Diabetic Society (JDS).

hplc method
To hemolyze the sample, we mixed 1.2 mL of diluted solution and 0.003 mL of blood cells in a 1.5-mL microtube. The sample was analyzed on the ADAMS-A1c HA-8160 (ARKRAY) based on the HPLC method. Calibration was performed daily with two calibrators containing different exclusive densities based on standard material established by the JDS.

immunoassay
To hemolyze the sample, we mixed 0.5 mL of diluted solution and 0.005 mL of blood cells in a 1.5-mL microtube. The sample was analyzed with an immunoassay (Rapidia-auto HbA1c; Fujirebio Inc.) on the automated analyzer (JCA-BM12). Calibration was performed daily with a calibrator containing five exclusive densities based on standard material established by JDS.

statistical analysis
Statistical analysis was performed with Excel 97 (Microsoft Corp.) software.


   Results
Top
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 References
 
within-run and total imprecision
Within-run imprecision was calculated by measuring three samples 20 times. The imprecision (CV) was 0.35% at a mean GHb of 4.2%, 0.22% at a mean GHb of 6.4%, and 0.19% at a mean GHb of 9.1%.

The total CVs for three samples measured over 20 days were 1.5%, 1.3%, and 1.1% at mean concentrations of 4.9%, 6.9%, and 10.2%.

linearity
Assay linearity was assessed by comparing the observed analytical values obtained for the proportional mixtures of the 4.5% and 15.9% samples. Linear regression analysis gave a relationship of: y = 1.0x - 0.1% (r = 0.998).

correlation between enzymatic assay and other methods
Regression analysis comparing the enzymatic assay (y) and the HPLC (x) method yielded the following: r = 0.979; slope, 0.994 [95% confidence interval (CI), 0.986–1.001]; y-intercept, 0.04% (95% CI, -0.09% to 0.01%); n = 2854. The mean difference between the measured values for these methods was -0.08% GHb, with a 95% CI of -0.67% to 0.50% GHb (Fig. 3 ).



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  		Figure 3. Correlation between the GHb values measured by the enzymatic assay and the HPLC assay (ADAMS-A1c HA-8160).

Data were obtained for blood cells from diabetes patients (n = 2854). (A), the regression equation for the enzymatic assay for GHb (y) compared with the on the ADAMS-A1c HA-8160 HPLC assay (x) is: y = 0.994x - 0.04%; r = 0.979. (B), Bland–Altman difference plot (enzymatic assay - HPLC assay) for paired means of the two methods. The mean difference between the methods was -0.08% GHb, with a 95% CI (dashed lines) of -0.67% to 0.50% GHb.

The correlation between the enzymatic assay (y) and the immunoassay (x) was r = 0.982 [slope, 1.002 (95% CI, 0.995–1.009); y-intercept, 0% (95% CI, -0.05% to 0.05%); n = 2854]. The mean change in value for these methods was 0.01% GHb, with a 95% CI of -0.54% to 0.56% GHb (Fig. 4 ). Because favorable correlation results were obtained, the measurement results for the enzymatic GHb method appear to be comparable to those of the conventional methods.



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  		Figure 4. Correlation between the GHb values measured by the enzymatic assay and the immunoassay (Rapidia HbA1c).

Data were obtained for blood cells from diabetes patients (n = 2854). (A), the regression equation for the enzymatic assay for GHb (y) compared with the Rapidia HbA1c immunoassay (x) is: y = 1.002x - 0%; r = 0.982. (B), Bland–Altman difference plot (enzymatic assay - immunoassay) for paired means of the two methods. The mean difference between the methods was 0.01% GHb, with a 95% CI (dashed lines) of -0.54% to 0.56% GHb.

reference interval
Reference values for nondiabetic persons are 4.3–5.8%, with a mean of 5.0%, as established by the JDS.

influence of Hb concentration
For this experiment, we used three samples in which GHb concentrations were 5.2%, 7.5%, and 9.8%, respectively, of the total Hb. We placed aliquots of blood cells from these samples (0.003, 0.005, 0.007, 0.01, 0.013, or 0.015 mL) in 1.5-mL microtubes, added 0.3 mL of Reagent 1, and hemolyzed the cells in a vortex-type mixer.

The influence of the Hb concentration on the measured GHb value was as follows (Fig. 5 ). Generally, as the amount of blood cells increased, the GHb value decreased. When the Hb concentration changed from 100 to 400 g/L, the GHb value changed from +0.4% to -0.4%. In other words, the measured value was not influenced when the Hb concentration in the sample increased 400%. Thus, whole blood with a Hb concentration of 50-200 g/L can be used as the specimen by changing the dilution rate.



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  		Figure 5. Influence of Hb concentration on GHb measurement.

The GHb concentration in the three samples was 5.2%, 7.5%, and 9.8%, respectively. The blood cells were hemolyzed by the addition of 0.3 mL of Reagent 1. The volume of blood cells was 0.003, 0.005, 0.007, 0.01, 0.013, or 0.015 mL. As the volume of blood cells increased, the GHb measured value decreased. When the concentration of Hb changed from 100 to 400 g/L, the measured GHb value changed from +0.4% to -0.4%.

influence of plasma
For this experiment, we used three samples with GHb concentrations of 4.7%, 7.0%, and 8.9%, respectively. We placed 0.01-mL portions of blood cells from these samples in 1.5-mL microtubes and added 0, 0.005, 0.01, 0.015, or 0.02 mL of plasma. We then added 0.3 mL of Reagent 1 to the microtubes and hemolyzed the cells in a vortex-type mixer.

The influence of plasma on the measured GHb value was as follows (Fig. 6 ). Generally, when plasma was added, the GHb value decreased. When 0.02 mL of plasma was added, the GHb value changed a maximum of -0.6%.



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  		Figure 6. Influence of plasma on GHb measurement.

The GHb concentration in the three samples was 4.7%, 7.0%, and 8.9%, respectively, of the total Hb. Blood cells (0.01 mL) and various amounts of plasma (0, 0.005, 0.01, 0.015, or 0.02 mL) were hemolyzed by the addition of 0.3 mL of Reagent 1. When plasma was added, the GHb value decreased. When 0.02 mL of plasma was added, the influence on the GHb measured value was -0.6% at the maximum. One milliliter of whole blood contains ~0.5 mL of plasma, but the measured value is influenced by <0.3%.

Because fructosamine in plasma was not measured, the measured value did not increase. When the specimen was whole blood, we increased the specimen volume by 0.02 mL. The sample included ~0.01 mL plasma, but the measured value was influenced <0.3%.

influence of interfering substances
For the interference experiments, we used three samples in which the GHb concentrations were 4.7%, 6.5%, and 9.0%, respectively. We placed 0.01 mL of blood cells from these samples in 1.5-mL microtubes and added a solution of interfering substances (0, 0.005, or 0.01 mL). We then added 0.3 mL of Reagent 1 to these samples and hemolyzed the mixtures in a vortex-type mixer.

The interfering substances and the maximum concentrations used were as follows: ascorbic acid (200 mg/L), uric acid (200 mg/L), glucose (10 g/L), albumin (100 g/L; A-8022; Sigma Chemical Co.), bilirubin (200 mg/L; International Reagents Corp.). The influence of the interfering substances on the GHb values was as follows. When ascorbic acid, glucose, or uric acid was added up to the maximum concentration, we found no influence on GHb. When 200 mg/L of bilirubin was added, the measured GHb value changed by -0.8%.

influence of sample preparation
Measured values were compared when the specimens were hemolyzed with Reagent 1 and analysis began 10 s, 5 min, and 30 min later, and when samples of blood cells were hemolyzed using an automated analyzer. The samples used in these experiments had GHb concentrations of 4.9% and 8.8%. The differences in measured values were within 0.1% GHb. The time variation between hemolysis and the beginning of analysis did not affect the measured values.


   Discussion
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
References
 
The enzymatic assay for GHb encompasses three new technologies, which are integrated into its three reagents.

The first new technology involves the development of the specific protease, which generates fructosyl amino acid only from Hb in blood. Even when plasma is added, no error occurs when this method is used. This means that other proteins in plasma, such as albumin and globulin, do not generate fructosyl amino acid. This new technology makes it possible to use both blood cells and whole blood as samples for the measurement. The specific protease resolves Hb in ~5 min and generates fructosyl amino acid.

The second technical advance is the development of FAOD, which reacts only with the fructosyl amino acid generated by the specific protease.

The third new technology involves the development of a method to detect H2O2 in the hemolysate with high sensitivity. When blood cells are hemolyzed, they release catalase and Hb. Catalase removes the H2O2, and Hb removes the color by decomposing the pigment. These factors cause a large negative error in the measured values. Interference from catalase was eliminated by the activation of POD instead of catalase. Hb is an undesirable interfering substance in serum analysis. With conventional measurement technologies, it was impossible to measure H2O2 in the hemolysate, so that GHb previously could not be measured by enzymatic methods. Interference from Hb was eliminated by combining WST-3, an original interference-removing agent, with Hb. The new technology makes it possible to detect even small amounts of H2O2 in the hemolysate. GHb can now be measured in the hemolysate without the need for separation and purification of the GHb.

The detection principle of the enzymatic assay is the detection of color produced by POD and H2O2. Because this method provides a rapid and uniform reaction in the same way as clinical biochemistry reagents (e.g., glucose or glutamic oxaloacetic transaminase), excellent precision was obtained with <1% error. In addition, with this method, GHb and Hb can be measured in the same cell; thus, the error that occurs with the use of an automated analyzer is reduced.

When a sample containing 7% GHb was measured by the conventional immunoassay method, the CV was 3.0%, so that ± 2 SD will be 0.84. This value of ± 2 SD (0.84) is greater than one-half of the reference interval. By contrast, the within-run CV of the new enzymatic assay is <0.5%, and the total CV is <1.5%. When a sample containing 7% GHb is measured, ± 2 SD will be 0.14 for within-run imprecision and 0.42 for total imprecision. This value is less than the medically allowable error [e.g., 1% GHb (17) and a CV of 3%, which is recommended by the National Glycohemoglobin Standardization Program (18)].

The conventional immunoassay with latex allows cells to deteriorate, and other measurements cannot be conducted on the same material. In contrast, the enzymatic assay does not influence other measurements, so that it can be used with other assays simultaneously on an automated analyzer, thus saving on both the labor and time required for the measurement.

In conclusion, the results produced by the enzymatic assay correlate favorably with those obtained with the conventional methods specific for HbA1c, such as the HPLC method and immunoassay, but the enzymatic assay provides a comparable or more precise result with a simple and rapid procedure that does not require expensive, dedicated instrumentation.


   Acknowledgments
 
We thank for Nobuo Kato and Yasuyoshi Sakai (Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University) and Yoshiki Tani and Nobuyuki Yoshida (Graduate School of Biological Science, Nara Institute of Science and Technology), who collaborated in the research and development of FAOD.


   Footnotes
 
1 Nonstandard abbreviations: GHb, glycohemoglobin; HbA1c, hemoglobin A1c; FAOD, fructosyl amino acid oxidase; POD, peroxidase; JDS, Japanese Diabetic Society; and CI, confidence interval.


   References
Top
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 References
 

  1. Gonen BA, Rubinstein AH, Rochman H, Tanega SP, Horwitz DL. Hemoglobin A1: an indicator of the metabolic control of diabetic patients. Lancet 1977;2:734-737.[ISI][Medline] [Order article via Infotrieve]
  2. Koenig RJ, Peterson CM, Kilo C, Cerami A, Williamson JR. Hemoglobin A1c as an indicator of the degree of glucose intolerance in diabetes. Diabetes 1976;25:230-232.[Abstract]
  3. . American Diabetes Association. Implications of the United Kingdom Prospective Diabetes Study (Position Statement). Diabetes Care 1999;22:27-31.[Abstract/Free Full Text]
  4. . American Diabetes Association. Tests of glycemia in diabetes [Position Statement]. Diabetes Care 1999;22:77-79.
  5. . Diabetes Control and Complications Trial Research Group. The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. N Engl J Med 1993;329:977-986.[Abstract/Free Full Text]
  6. . Diabetes Control and Complications Trial Research Group. The absence of a glycemic threshold for the development of long-term complications: The perspective of the diabetes control and complications trial. Diabetes 1996;45:1289-1298.[Abstract]
  7. John WG, Braconnier F, Miedema K, Aulesa C, Piras G. Evaluation of the Menarini-Arkray HA 8140 hemoglobin A1c analyzer. Clin Chem 1997;43:968-975.[Abstract/Free Full Text]
  8. Chevenne D, Marle N, Chauffert M, Noel M, Ducrocq R, Trivan F. Evaluation of Tosoh HLC-723GHb V A1c 2.2 hemoglobin A1c analyzer. Clin Biochem 1999;32:487-490.[CrossRef][ISI][Medline] [Order article via Infotrieve]
  9. Blakney GB, Higgins TN, Holmes DJ. Comparison of hemoglobin A1c results by two different methods on patients with structural hemoglobin variants. Clin Biochem 1998;31:619-626.[CrossRef][ISI][Medline] [Order article via Infotrieve]
  10. Halwachs-Baumann G, Katzensteiner S, Schnedl W, Purstner P, Pieber T, Wilders-Truschnig M. Comparative evaluation of three assay systems for automated determination of hemoglobin A1c. Clin Chem 1997;43:511-517.[Abstract/Free Full Text]
  11. Weets I, Frans K, Gerlo E. Evaluation of an immunoturbidimetric assay for haemoglobin A1c on a Cobas Mira S analyser. Eur J Clin Chem Clin Biochem 1995;34:449-453.
  12. Metus P, Ruzzante N, Bonvicini P, Meneghetti M, Zaninotto M, Plebani M. Immunoturbidimetric assay of glycated hemoglobin. J Clin Lab Anal 1999;13:5-8.[CrossRef][ISI][Medline] [Order article via Infotrieve]
  13. John WG, Gray MR, Bates DL, Beachem JL. Enzyme immunoassay—a new technique for estimating haemoglobin A1c. Clin Chem 1993;39:663-666.[Abstract/Free Full Text]
  14. Yoshida N, Sakai Y, Isogai A, Fukuya H, Yagi M, Tani Y, et al. Primary structures of fungal fructosyl amino acid oxidases and their application to the measurement of glycated proteins. Eur J Biochem 1996;242:499-505.[ISI][Medline] [Order article via Infotrieve]
  15. Sakai Y, Yoshida N, Tani Y, Kato N. Production of fructosyl lysine oxidase from Fusarium oxysporum S-1F4 on autoclave-browned medium. Biosci Biotech Biochem 1996;60:150-151.[Medline] [Order article via Infotrieve]
  16. Yoshida N, Sakai Y, Serata M, Tani Y, Kato N. Distribution and properties of fructosyl amino acid oxidase in fungi. Appl Environ Microbiol 1995;61:4487-4489.[Abstract]
  17. Larsen ML, Petersen PH, Fraser CG. Quality specification for haemoglobin A1c assays in the monitoring of diabetes. Upsala J Med Sci 1993;98:335-338.[ISI][Medline] [Order article via Infotrieve]
  18. Little RR, Rohlfing CL, Wiedmeyer HM, Myers GL, Sacks DB, Goldstein DE, . the NGSP Steering Committee. The National Glycohemoglobin Standardization Program: a five-year progress report. Clin Chem 2001;47:1985-1992.[Abstract/Free Full Text]




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