Comparability of hemoglobin A1c level measured in capillary versus venous blood sample applying two point-of-care instruments

Abstract

Background: The present study is designed to evaluate the validity of the measurement of capillary blood hemoglobin A1c levels in comparison with venous blood hemoglobin A1c. Methods: The data of this cross-sectional study are collected from a sample of 45 Iranian diabetic patients referred to one particular laboratory for the assessment of HbA1c level during a period from April to December 2013. Venous and simultaneous capillary blood samples were obtained from each subject for measurement of hemoglobin A1c levels. Both samples were tested using two different NGSP certified systems: CERA STAT 2000 (Ceragem Medisys Inc) and NycoCard Reader II (Axis-Shield). Results: The mean hemoglobin A1c in venous and capillary blood samples measured using CERA STAT 2000 assays were 6.30 ± 1.68% and 6.34 ± 1.65% respectively (p = 0.590). However, when NycoCard Reader II assay was employed, the mean hemoglobin A1c in venous and capillary blood samples were 6.73 ± 1.35% and 6.92 ± 1.50% (p = 0.007). Moreover, a strong correlation was observed between venous and capillary hemoglobin A1c levels with Pearson's concordance correlation coefficients of 0.96 and 0.94 with the use of NycoCard Reader II and CERA STAT 2000 assays respectively. Application of CERA STAT 2000 demonstrated to be of a considerably higher value using the ROC curve analysis assay (AUC = 0.991). Also, similar analysis by using NycoCard Reader II assay demonstrated that capillary hemoglobin A1c measurement had high value for differentiation of uncontrolled from controlled blood glucose level (AUC = 0.935). Conclusion: It was demonstrated that capillary hemoglobin A1c measurement had a considerably high value for differentiating between poorly-controlled and well-controlled blood glucose levels.