Hemoglobin A1c: a reliable and accurate test for diabetes care? A prospective study in Mexico.

OBJECTIVE To compare the concordance correlation coefficient for HbA1c results in an in-field experience. MATERIALS AND METHODS A prospective study in Monterrey, Mexico from April to August 2012 was conducted to evaluate the day-to-day clinical situation when measuring HbA1c. Blood samples from 38 consecutive patients were sent to seven local laboratories and one international reference laboratory. RESULTS Poor concordance was found in 4 out of 7 laboratories, moderate in 2 out of 7, and significant in just one. HbA1c values from three laboratories fluctuated more than 1% above or below the reference laboratory in more than 30% of cases, and more than 2% in 10%-20% of subjects. CONCLUSIONS Standardized HbA1c measurement has not occurred worldwide. Physicians should be aware of this issue and be cautious of HbA1c guidelines on diabetes diagnosis or management until proper standardization programs are implemented.