Effect of hemoglobinopathies on hemoglobin A1c measurements

Total hemoglobin count has significant impact on A1C - Data from National Health and Nutrition Examination Survey 1999-2014

BACKGROUND

Previous study showed A1C was affected by hemoglobin and gender in non-anemic Koreans. However, there was no other data to support those important findings.

METHODS

Participants from National Health and Nutrition Examination Survey (NHANES) - 1999 to 2014 with age over 12 years were examined. After excluding participants with hypoglycemia and moderate to severe anemia, 22,974 participants were included in analysis. Both female and male were divided into three groups based on their hemoglobin level. Linear regression and multivariate regression analyses were conducted to assess the relationship between A1C and hemoglobin in three fasting plasma glucose (FPG) intervals.

RESULTS

For both female and male, A1C was significantly negatively correlated with hemoglobin in the FPG interval range between 80 to 126mg/dl, p<0.0001. A1C was not significantly associated with hemoglobin over the other two intervals (70≤FPG<80mg/dl and FPG≥126mg/dl, p>0.05). In addition, over FPG interval between 80 to 126mg/dl, after adjusting age and fasting glucose level, A1C still significantly negatively correlated with hemoglobin (regression coefficient=-0.052, p<0.0001 in females, regression coefficient=-0.050, p<0.0001 in males).

CONCLUSIONS

A1C would decrease by 0.05% (about 0.5mmol/mol) as a result of each 1g/dl increase in total hemoglobin count when plasma glucose level in normal or prediabetes range. The mechanism behind this finding is unclear. Further study should be conducted and hemoglobin count may need be taken into consideration when applying A1C for the diagnosis of diabetes or to screen for prediabetes.

A spuriously ‘normal’ haemoglobin A1c result

We report a case of spuriously ‘normal’ haemoglobin A1c (HbA1c) result due to misidentification of HbG Taipei as HbAo by the Variant II built-in retention time algorithm. The defect was circumvented effectively by the implementation of a chromatographic system specific internal quality control mechanism for peak identity verification. HbA1c and estimated average glucose results were corrected from 4.7% to 8.2%, and 4.9 to 10.5 mmol/L, respectively. The results were consistent with the patient's concurrent and previous fasting blood glucose concentrations and existence of diabetes mellitus dermopathy, indicating poor glycaemic control. A review of currently available analytical systems showed that other than mass spectrometry, HbA1c measurements by these systems were generally affected by the presence of haemoglobin variants. The same haemoglobin variant may affect different analytical systems differently, resulting in the deviation of HbA1c results from the true value to different extents. Including the analytical principle of HbA1c measurement in the laboratory report can avoid inappropriate comparison of results obtained by different analytical systems. Moreover, since individual haemoglobinopathy may affect the degree of glucose binding to haemoglobin in a different way, this uncertainty limits the general application of same decision cut-off of established guidelines for glycaemic control monitoring. Adoption of an individualized monitoring system based on the critical difference or reference change value of HbA1c can be considered.

Hemoglobin variants detected by hemoglobin A1c (HbA1c) analysis and the effects on HbA1c measurements

Background:

Hemoglobin (Hb) A1c is a tool widely used to monitor long-term glycemic control in diabetic patients. The objective of our study is to compare the HbA1c values measured on high performance liquid chromatography (HPLC) and immunoassay in patients who were detected to have hemoglobin variant after HbA1c analysis.

Materials and Methods:

We compared the HbA1c values measured using the Arkray Adams A1c HA-8160 (HPLC method) and Roche Cobas Integra (immunoturbidimetric method) from diabetic patients who were diagnosed with hemoglobin variants.

Results:

Forty-three diabetic patients were diagnosed with hemoglobin variants: 13 elevated Hb F, 12 Hb E trait, seven Hb S trait, seven Hb D trait, two Hb E / beta-Thalassemia, one Hb C trait, and one homozygous Hb S.

Conclusion:

Knowledge of hemoglobin variants affecting HbA1c measurements is essential, in order to avoid mismanagement of diabetic patients.