Relationships between hemoglobin A 1c and spot glucose measurements in Nigerians with type 2 diabetes mellitus

BACKGROUND: Glycosylated hemoglobin, HbA 1c is the most acceptable measure of chronic glycemia. It is not widely available and/or affordable in Nigeria. The mean of the monthly fasting plasma glucose (MFPG) of the preceding 3 months is often used as surrogate for assessing chronic glycemia. OBJECTIVE: To determine the relationships among fasting plasma glucose (FPG), 2-hour post-prandial glucose (2-hPG), HbA1c, and MFPG. MATERIALS AND METHODS: Hospital records were used to derive the MFPGs of diabetic subjects from the mean of their monthly FPGs of the preceding three months. Other data extracted included the patient's age, sex, body mass index (BMI), waist circumference (WC), and duration of diabetes mellitus (DMDU). FPG, 2- hPG and HbA 1c were determined during this index consultation. RESULTS: Ninety five persons (65 males, 30 females) with type 2 were included in the study. Their mean age and DMDU were 54.7 ± 8.9 years and 8.1 ± 6.1 years, respectively. Their mean WC, BMI, FPG, 2-hPG, HbA1c, and MFPG were 100.2 ± 11.0 cm, 24.2 ± 4.3 kgm/2, 7.5 ± 2.4 mmol/l, 10.4 ± 4.1 mmol/l, 8.2 ± 2.2%, and 5.9 ± 2.2 mmol/l, respectively. The males were significantly older (57.5 ± 8.4 vs 49.3 ± 7.6, P<0.001) while the females had higher waist circumference and BMI than their male counterparts: 104.8 ± 11.6 cm vs 92.8 ± 10.1 cm, P<0.004; and 25.8 ± 4.9 kg/m 2 vs 23.3 ± 3.7 kg/m 2 , P<0.005, respectively. There were no significant differences in FPG, 2-hPG, MFPG and HbA1c levels between male and female subjects. There were significant positive correlations between FPG and HbA1c (r=0.45, P=0.05) and between 2-hPG and HbA1c (r=0.52, P=0.01), but there was no positive correlation between MFPG and HbA1c (r=-0.20, P=0.18). CONCLUSION: There is no positive correlation between MFPG and HbA 1c and thus MFPG may not be a good surrogate for HbA1c in assessment of chronic glycemia in our patients.