A collaborative study of the measurement of glycosylated haemoglobin by several methods in seven laboratories in the United Kingdom

Abstract

A collaborative study compared methods for measuring glycosylated haemoglobin in seven laboratories in the United Kingdom. No satisfactory standard for general use was found. Satisfactory internal quality control systems were in use for each assay which allowed the maintenance of a normal range in each participating laboratory. No satisfactory quality control system suitable for general use could be identified. Costs and convenience of the assays are reported. The technical problems with each type of assay and precautions for their use were identified, such as the need for standardization in incubation times, the practicability of automation of colorimetric assays, and the precision of pH needed for buffers in column separation methods. The relevance of the technical problems to interpretation of measurements is also considered. It is concluded that laboratories measuring glycosylated haemoglobin should maintain a normal range, use 'in-house' quality controls to monitor assay performance and keep clinical colleagues informed of the findings and of any changes in methodology that might affect the interpretation of results.

Glycated Haemoglobin Analyses—Assessment of within- and between-Laboratory Performance in a Large UK Region

“…This finding constrasts with that described by Boucher et aJ. 11 who reported that this group produced the highest results and suggested that this may have been due to the Schiff base which they did not remove. In this present study, the Schiff base was removed by distributing red cells in saline, introducing an overnight incubation step whilst specimens were in the post.…”

“…Precision (on distributed duplicate specimens) agrees with that previously reported. 11 Within-Iaboratory/between-batch precision usingfrozen haemolysates was poor for electroendosmosis and ion-exchange chromatography, mainly due to the instability of that type of specimen. Frozen haemolysates can therefore only be used to assess affinity chromatography methods.…”

In vitro determination of hemoglobin A1c for diabetes diagnosis and management: technology update

“…33,34 The disparate results obtained were because of the range of methods being used by laboratories, the lack of standardization, and lack of a primary reference material. Although the new generation of HbA 1c methods now demonstrate a degree of precision that could not be imagined 30 years ago, comparison of results from different laboratories would remain, at best, difficult -or, more likely, impossible -if not for standardization schemes.…”

IFCC standardised HbA1c: should the world be as one?

“…Following the introduction of HbA 1c methods into routine clinical practice around 1977, it quickly became apparent that there was a signifi cant difference in the results produced by different laboratories (8) with a between laboratory coeffi cient of variation (CV) of 11.2 % -20.1 % observed (9) . It was evident that the disparate results obtained were because of the range of methods being used by laboratories, the lack of standardisation and no primary reference material.…”