Next Generation Glycated Hemoglobin Assay Evaluated

Diabetes mellitus is a pathological condition that affects all age groups worldwide. The percentage of glycated hemoglobin A1C (HbA_1C) reflects the mean plasma glucose level over the previous 3 to 4 months for most individuals and can be used to diagnose type 2 diabetes.

Immunoassay has become an accepted approach for the measurement of HbA_1C. Following the on-board detergent-induced lysis of whole blood samples, the amount of HbA_1C is quantified by the binding of an antibody to HbA molecules that are glycated at the N-terminus of their β-chain. This amount is compared to the total concentration of Hb in the sample determined by absorbance values and a percent HbA_1C is calculated.

Medical Laboratorians at the University of Calgary (Calgary, AB, Canada) and their associates evaluated the performance characteristics of the Roche Cobas c 513 (Roche Diagnostics, Basel, Switzerland), a stand-alone next generation immunoassay analyzer for HbA_1C. They assessed the imprecision, accuracy, analytical measuring range, and throughput of this instrument. Method comparisons studies were performed against a previous generation immunoassay analyzer (Roche Integra 800 CTS). They also studied the effects of erythrocyte sedimentation and potential interference from hemoglobin variants.

The method comparison of the c 513 whole blood or hemolysate application to the Integra 800 CTS assay was performed using 40 fresh EDTA whole blood samples distributed across the reportable range of the HbA_1c assay retrieved after routine measurement. The effect of sedimentation of whole blood samples on the measurement of %HbA_1C was investigated by re-assaying 30 unmixed samples 24 hours after the initial mixing. These samples ranged from 4.5-15.5 %HbA_1C (median value, 11.9 %HbA_1C). The effect of potentially interfering hemoglobin variants on the HbA_1C measurement was investigated by assaying patient samples (N = 6–36) containing heterozygous HbS, HbC, HbE, HbD, or HbJ or elevated levels of HbF (6.8–29.9%) on the c 513, Integra 800 CTS, and Variant II Turbo 2.0 (Bio-Rad, Hercules, CA, USA).

The scientists reported that the within-run and between-run precisions were 0.5–0.7 and 0.8–1.3%CV, respectively. An average bias of -1.6% to proficiency survey samples was observed. The c 513 correlated well with the Integra (slope = 0.94, y-intercept = 0.50, and correlation coefficient = 0.998). The effect of hemoglobin variants on this assay was negligible while specimens containing ≥10% HbF demonstrated a negative bias. The c 513 instrument can process up to 340 samples per hour.

The authors concluded that their data supports the routine use of the c 513 for %HbA_1C quantification by the clinical laboratory. The assay is precise and accurate and the instrument is capable of testing of more than 7,500 specimens in 24 hours. While care must be taken to ensure correct sample processing is followed, this instrument is a good solution for large references laboratories with HbA_1C volumes of 1,500 per day or higher. The c 513 is a precise, accurate, automated high throughput analyzer for measuring HbA_1C in large laboratories. The study was published on November 9, 2019 in the journal Practical Laboratory Medicine.


Related Links:
University of Calgary
Roche Diagnostics
Bio-Rad