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Background: The aim of our study was to evaluate three POC instruments for the measurement of glycated hemo- globin (HbA1c) (Cobas b101 (Roche Diagnostics®), Afinion TM (Alere Technologies), and B-analyst (Menarini Di- agnostics)), which were compared to G8 (Tosoh®) as the reference method. In addition, the inter-assay and intra- assay variability, and linearity of the different techniques were analyzed.
Methods: Method comparison was performed according to Clinical and Laboratory Standards Institute (CLSI) EP9-A2 guidelines. We selected 100 samples from the routine laboratory workload and analyzed them in dupli- cate with the three analyzers, as well as with the reference method. The imprecision study was performed accord- ing to CLSI EP5-A2 guidelines for both inter-assay and intra-assay variability. The inter-assay variability was es- timated from aliquots of a sample obtained from a blood pool with an HbA1c value of 6.1% as determined by the reference method. To establish linearity, the CLSI EP6-A protocol was followed.
Results: Method comparison (95% confidence intervals in parentheses): Passing-Bablok regression between the Cobas b101 and the G8, the slope was 0.886 (0.865, 0.909), y-intercept: 0.80 (0.61, 0.96), r = 0.99 (p < 0.05). Bland- Altman mean difference: -0.0985 (-0.0171, -0.0264). In the case of the Afinion, slope 0.967 (0.938, 1.000), y-inter- cept 0.263 (0.000, 0.475), r = 0.984, Bland-Altman mean difference: 0.0178 (-0.0561, 0.0917) and finally in the case of B-analyst compared to the G8 the slope: 1.036 (1.000, 1.056), y-intercept: -0.14 (-0.30, 0.10), r = 0.996 Bland-Alt- man mean difference: 0.124 (0.0851, 0.162). The values for CV% obtained for Cobas b101, Afinion, and B-Analyst were, respectively, for inter-assay coefficient of variation (CV): 1.92%, 2.13%, 1.34%, for intra-assay CV: 2.06%, 1.13%, 1.79% (low level), and 1.87%, 1.97%, 3.17% (high level). The three methods studied are linear in the test interval.
Conclusions: The results of this study show that the Cobas b101, Afinion, and B-analyst instruments present a good correlation with the reference method. In summary, the three POC HbA1c devices assessed offer the advan- tages of fast and reliable test results that make their use possible to improve the care of diabetic patients as well as the possibility of establishing early treatment because of their immediate availability. They are therefore consid- ered suitable for the control, but not for the diagnosis of diabetes.
DOI: 10.7754/Clin.Lab.2017.161212
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