HbA1c is used for assessing glycaemic control in patients with diabetes. It is also used for treatment goals and as a target for therapeutic intervention. The Direct Control and Complications Trial in the USA showed that HbA1c can be used to predict the risk of complications. Hence, it is important for HbA1c assays to be standardised. The National Glycohemoglobin Standardization Program (NGSP) in the USA was formed in 1996 so that HbA1c results from different laboratories would be comparable to those reported in the DCCT study. There were also HbA1c standardisation programmes in Sweden and Japan. These three standardisation programmes are, in fact, direct comparison methods (DCMs), and yield different HbA1c results. In 1994, the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) established a Working Group on Standardisation of HbA1c. This working group has developed a global HbA1c reference system with very much improved intra-assay and inter-assay coefficients of variation. Recommendations have been made to report HbA1c results as IFCC-HbA1c values in SI units (mmol HbA1c/mol Hb) and NGSP-HbA1c (%) as well as estimated average glucose (eAG), once a tight relationship has been shown to exist between eAG and HbA1c.
The Asian Network for Clinical Laboratory Standardization (ANCLS) decided to start her First Inter-laboratory Quality Assurance survey at the business meeting during the Second Asian Colloquium on October 21-22, 2000 in Kobe, Japan. The first survey materials of Asian Quality Assurance Survey (AQuAS) were distributed in July 2001 to 21 hospitals in the field of chemistry and 22 hospitals in the field of hematology among total 24 participating laboratories from seven Asian countries: Indonesia, Japan, Korea, Malaysia, Philippines, Singapore and Thailand. The survey methods in chemistry and in hematology were somewhat different. In chemistry the survey material was considered as unknown but handled similarly to the sample from the patient. Nineteen routine tests were performed only once. The hematology samples were considered as unknown but handled similarly to control or calibration material. Five parameters were tested five times repetitively and their average for each parameter was calculated. All the results were supposed to be sent back to the office within two weeks. Although it took more than two weeks, the return rate was 100%. The analysis was performed in several ways such as all the results together, by instruments and by methods. Mean, standard deviation (SD), standard deviation index (SDI), coefficient of variation (CV) and variance index score (VIS) were to be calculated in chemistry, and in hematology the same parameter were to be calculated except CV and VIS. In the first survey, the CV in chemistry was not calculated and the analysis by instrument or by methodology was also not attempted since there were not enough participating hospitals to do such analysis. In hematology the analysis was done by instrument only. The survey process was carried out successfully though there were some difficulties in communication tools, transportation methods and handling of specimens due to different weather conditions, and returning the report in the correct unit and to the correct place. The submitted data were acceptable for analysis. There were some differences in the units of measurement in different countries or laboratories. It was necessary to convert some of the units. Some laboratories apparently do not perform certain tests such as calcium, potasium and gamma-glutamyltransferase (gamma-GT). The gamma-GT is the most frequently not performed test. With the experience of this first survey, all the members involved in the survey have been trained well to do future surveys.
HbA1c measurement is currently routinely used to predict long term outcome of diabetes, thus playing a fundamental role in the management of diabetes. The relationship between HbA1c value and long term diabetic complications has been established by a randomised control Diabetes Control and Complications Trial (DCCT) which used high performance liquid chromatography (HPLC) as a reference method for HbA1c assay. To ensure that HbA1c results from a variety HbA1c assay methods are similar to the DCCT values, the American Diabetes Association (ADA) recommended that all laboratories should use methods certified by the National Glycohemoglobin Standardization Programme (NGSP) with interassay coefficient variation (CV) of < 5% (ideally < 3%). The International Federation of Clinical Chemistry (IFCC) working group on HbA1c standardisation has set a CV < 2.5% as a criteria for its reference laboratories.