Objective: To establish HbA1C reference intervals according to DCCT/NGSP (HbA1C DCCT/NGSP) and IFCC (HbA1C IFCC) in adults.
Study Design: The study was a descriptive study.
Material and Method: The study was done in 144 subjects, with 99 males and 45 females, aged between 19 to 78 years old. All subjects had normal vital signs, physical examination, chest X-ray. Subjects who had hyperglycemia, renal problem, liver problem, anemia, and/or hemoglobinopathy were excluded from the present study.
Results: Reference intervals of HbA1C (DCCT/NGSP) is 5.47% (4.79-6.15) and HbA1C (IFCC) is 3.66% (2.88-4.44). The authors also found very high correlation between HbA1C (DCCT/NGSP) and HbA1C (IFCC) of total, male, female, < 35 years old, and > 35 years old, r = 0.9995, 09997, 0.9992, 0.9988, and 0.9999, respectively.
Conclusion: The authors found that HbA1C (DCCT/NGSP) and HbA1C (IFCC) are not affected by sex but are influenced significantly by age group. Since HbA1C (IFCC) will be widely used in routine diabetes management, the authors recommend all laboratories provide the results of HbA1C in both DCCT/NGSP and IFCC methods during this interim period.

Keywords: HbA1C (DCCT/NGSP), HbA1C (IFCC), Reference intervals