HbA1c levels measured by enzymatic assay during off-site health checkups are lower than those measured by on-site HPLC assay

HbA1c is widely used as a therapeutic target marker and as a diagnostic marker for diabetes mellitus. This has led to an increasing frequency of HbA1c measurements in current health checkups throughout Japan. In the present study, we compared the HbA1c levels measured by an enzymatic assay (EA-HbA1c) off-site during health checkups with the HbA1c levels measured by on-site ion-exchange high-performance liquid chromatography (HPLC; HPLC-HbA1c) in a hospital. A total of 96 individuals (53 males and 43 females; age, 68.9 ± 8.4 years old; 70 diabetic and 26 non-diabetic individuals) whose HbA1c levels were measured by both the methods listed above were included in the study. Since no HPLC-HbA1c levels were measured on the day of the health checkup, HPLC-HbA1c levels were estimated using HPLC-HbA1c levels measured before and after the health checkup. A significant correlation of HbA1c levels was observed between the two groups (R = 0.973; p < 0.001). However, EA-HbA1c levels measured off-site during health checkups are lower than estimated HPLC-HbA1c levels measured on-site (6.37 ± 0.75% vs. 6.69 ± 0.75%; p < 0.001). Since lower EA-HbA1c levels measured during health checkups, which diverged from on-site measurements, may lead to underestimating diabetes mellitus, accurate measurement of HbA1c is required irrespective of the measuring method. Further investigation of the cause of falsely low EA-HbA1c levels and the strategy for reconciling HbA1c to reflect plasma glucose accurately are warranted.