External Quality Assessment of Glycated Hemoglobin in Iran: Comparison of Five Different Commercial Methods with Two...

Glycated hemoglobin (HbA_1c) measuring has a critical role in the monitoring and diagnosis of diabetes. So, the analytical performance of its measuring method must be acceptable. Clinical laboratories should continuously monitor the performance of their commercial methods, both by using proper internal quality control (IQC) and by participating in external quality assessment schemes (EQAS).

In January and August 2016, two different freshly prepared commutable patient QC samples were sent to over 1000 laboratories, but 682 and 925 different laboratories which were used five common commercial methods for measuring HbA_1c, included in this study during 23^th and 24^th runs of the external quality assessment program (EQAP), respectively. Target values for total group and also for peer groups were calculated. The performance of each method and laboratory were determined according to two different allowable total errors (TEa), including ±6% and ±20%, which are suggested by the National Glycohemoglobin Standardization Program (NGSP) and Reference Health Laboratory of Iran, respectively.

Considering TEa of ±20% in evaluating HbA_1c commercial methods and laboratory performances, pass rates ranged from 97% to 98% during EQAP-23 and EQAP-24, respectively. But when this evaluation was performed according to TEa of ±6%, pass rates decreased significantly to 60% and 62%, respectively.

Using improper analytical goals has led to misinterpretation of EQA results. In order to maintain the clinical usefulness of HbA_1c results, we need to reduce TEa of ±20% to ±6% and improve HbA_1c measuring method performance. Although, with TEa of ±6% our pass rates are not so bad.