Letter to the Editor regarding "Achieving comparability with IFCC reference method for the measurement of hemoglobin A1c by use of an improved isotope-dilution mass spectrometry method"

External quality assessment scheme for HbA1c assays in Thailand: A 5-year experience

Background

Thailand National External Quality Assessment Scheme (NEQAS) for HbA1c was established to evaluate the quality of HbA1c assays in Thailand in 2016.

Methods

HbA1c results from participating laboratories were compared to the target value assigned by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) reference system.

Results

The pass rates of participating laboratories during 2016–2020 were72–88%. The mean bias ranged between −0.19 and 0.20% of HbA1c. SD ranged from 0.30 to 1.08% of HbA1c. The overall coefficients of variation ranged from 4.46-15.66%.

Conclusions

Performance evaluation using IFCC assigned values indicated that different assay methods had an effect on HbA1c results. Participation in external quality assessment programs for HbA1c analysis is essential for improving laboratory quality and benefiting patient management.

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This study summarized the performance evaluation of HbA1c assays using IFCC assigned values during a 5 year period in Thailand.

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The most interesting finding was that the quality of HbA1c analysis varied depending on the assay method used.

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This finding should encourage clinical laboratories, manufacturers, and proficiency testing providers to work together to improve laboratory quality.

Accuracy of HbA1c as Monitored by External Quality Assessment and Compared With Patient Mean Values

BACKGROUND

The accuracy and trueness of results from a laboratory test, such as the HbA1c test, should not be taken for granted but must be checked continuously. A tool for this is the participation in external quality assessment (EQA) for all laboratories performing the HbA1c-test. An additional possibility to detect changes in trueness is to monitor variations in patient cohort mean or median values that is not explained by changes in treatment or selection of patients.

METHODS

Results reported to an EQA scheme for HbA1c during 20 years have been extracted from Equalis database. The results are compared to current analytical performance specifications (APS) and to the mean HbA1c levels for the Swedish population of persons with type 2 diabetes.

RESULTS

The accuracy of the HbA1c test has improved during the period. The hospital lab methods used in Sweden now fulfil APS agreed by professional organizations in Sweden. The accuracy for point-of-care tests (POCT) methods vary over time and fulfil APS for some periods. The bias found for some of the methods might explain changes seen in patient mean values for HbA1c in Sweden during the period 2007-2017.

CONCLUSIONS

The global standardization of HbA1c has resulted in an improved comparability for HbA1c-results worldwide. But even small variation in trueness for the methods in use might have important impact on mean HbA1c values for cohorts of patients. When a systematic error is observed for a specific method it is therefore essential that manufacturers correct the method without delay.