Effect of calibration on dispersion of glycohemoglobin values determined by 111 laboratories using 21 methods

Abstract

One hundred eleven laboratories, using 21 different methods based on five different principles, determined glycohemoglobin (GHb) percentages in two identical series of six lyophilized hemolysates and three similarly processed calibrators, distributed 3 months apart. To assign GHb percentages to calibrators, we used HbA1c results from nine participants who used the Bio-Rad Diamat high-performance liquid chromatographic method. Three-point calibration with assigned values improved mean intralaboratory variation (CV) from 6.6% to 3.5%. For samples with low (5.5%) and high (14.1%) GHb percentages, respectively, calibration decreased interlaboratory variation per method (from 10% to 4% and from 6% to 3%), inter-method variation (from 18% to 4% and from 16% to 3%), and overall interlaboratory variation (from 25% to 7% and from 15% to 4%). Without calibration, 71% of the laboratories did not meet the clinically desirable intralaboratory CV of 3.5%; calibration reduced this proportion to 39%. We conclude that, irrespective of the analytical method used, calibration greatly reduces all sources of GHb variation.

Detection and characterization of variant and modified structures of proteins in blood and tissues by mass spectrometry

“…Each method is calibrated using reference materials that are adjusted to an international reference material. Unfortunately, considerable discrepancies in the measured values of HbA 1c have been observed among methods and among laboratories (Weykamp et al, 1994). The International Federation of Clinical Chemistry (IFCC) proposed an approved reference method for measurement of HbA 1c applying LC‐ESI‐MS (Jeppsson et al, 2002).…”

Hemoglobin A(1c) Reporting Units and Diagnostic Cut-Offs in Relation to International Recommendations

“…Later in the 1960s, measurement of the hemoglobin A(1c) fraction by qualitative or quantitative assays began when Trivelli & al. published the first quantitative assay of HbA(1c) [3,4]. Numerous methods have then been developed for HbA(1c) measurements [2,[4][5][6][7]. Weykamp & al concluded that the high variation between the methods and the laboratories was substantially corrected by a new calculation of the primary results [5].…”

“…Numerous methods have then been developed for HbA(1c) measurements [2,[4][5][6][7]. Weykamp & al concluded that the high variation between the methods and the laboratories was substantially corrected by a new calculation of the primary results [5].…”

Comparative evaluation of three different methods for HbA 1c measurement with High-performance liquid chromatography in diabetic patients

“…[ 6 12 13 14 ] In addition, calibration based on HPLC has been proven to enhance comparability among the various methods. [ 11 15 ] Many specialists are not well satisfied due to the inconsistency of HbA 1C , reported through various methods, with patients’ values attained by a reference method (HPLC). On the one hand, the HPLC device is very expensive, difficult and time consuming to work with; therefore, it needs professional personnel to work with, consequently making it impossible and not cost-effective for all laboratories.…”