Stability of glycated haemoglobin (HbA1c) measurements from whole blood samples kept at -196°C for seven to eight years in The Malaysian Cohort study.

OBJECTIVE: Glycated haemoglobin (HbA1c) is a standard indication for screening type 2 diabetes that also has been widely used in large-scale epidemiological studies. However, its long-term quality (in terms of reproducibility) stored in liquid nitrogen is still unknown. This study is aimed to evaluate the stability and reproducibility of HbA1c measurements from frozen whole blood samples kept at -196°C for more than 7 years. METHODS: A total of 401 whole blood samples with a fresh HbA1c measurement were randomly selected from The Malaysian Cohort's (TMC) biobank. The HbA1c measurements of fresh and frozen (stored for 7-8 years) samples were assayed using different high-performance liquid chromatography (HPLC) systems. The HbA1c values of the fresh samples were then calculated and corrected according to the later system. The reproducibility of HbA1c measurements between calculated-fresh and frozen samples was assessed using a Passing-Bablok linear regression model. The Bland-Altman plot was then used to evaluate the concordance of HbA1c values. RESULTS: The different HPLC systems highly correlated (r = 0.99) and agreed (ICC = 0.96) with each other. Furthermore, the HbA1c measurements for frozen samples strongly correlate with the corrected HbA1c values of the fresh samples (r = 0.875) with a mean difference of -0.02 (SD: -0.38 to 0.38). Although the mean difference is small, discrepancies were observed within the diabetic and non-diabetic samples. CONCLUSION: These data demonstrate that the HbA1c measurements between fresh and frozen samples are highly correlated and reproducible.

Cardiovascular risk prediction with cardio-ankle vascular index in the malaysian cohort study.

The cardio-ankle vascular index (CAVI) is an important parameter assessing arterial function. It reflects arterial stiffness from the origin of the aorta to the ankle, and the algorithm is blood pressure independent. Recent data have suggested that a high CAVI score can predict future cardiovascular disease (CVD) events; however, to date, no study has been done in Malaysia. We conducted a prospective study on 2,168 The Malaysian Cohort (TMC) CVD-free participants (971 men and 1,197 women; mean age 51.64 ± 8.38 years old) recruited from November 2011 to March 2012. This participants were followed-up until the emergence of CVD incidence and mortality (endpoint between May to September 2019; duration of 7.5 years). Eligible participants were assessed based on CAVI baseline measurement which categorised them into low (CAVI <9.0) and high (CAVI ≥ 9.0) scores. The CVD events in the group with high CAVI (6.5 %) were significantly higher than in the low CAVI (2.6 %) group (p < 0.05). CAVI with cut-off point ≥ 9.0 was a significant independent predictor for CVD event even after adjustment for male, ethnicity, age, and intermediate atherogenic index of plasma (AIP). Those who have higher CAVI have 78 % significantly higher risk of developing CVD compared to those with the low CAVI (adjusted OR [95 % CI] = 1.78 [1.04 - 3.05], p =0.035). In addition, the participants with higher CAVI have significantly lower survival probability than those who have lower CAVI values. Thus, this study indicated that the CAVI can predict CVD event independently among the TMC participants.