Biomarker of Chronic Alcohol Abuse – Carbohydrate-deficient Transferrin (CDT): Methodology Verification

Gomes, Filomena; Costa, Alcina; Fernandes, Lília; Silva, Ana Maria V. da; Vasconcelos, Miguel; Miranda, Armandina

http://hdl.handle.net/10400.18/8866

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Authors

Gomes, Filomena

Costa, Alcina

Fernandes, Lília

Silva, Ana Maria V. da

Vasconcelos, Miguel

Miranda, Armandina

Abstract(s)

Introduction: Transferrin is a glycoprotein synthesized in hepatocytes that can appear with different isomorphic forms in the plasma, acquiring different levels of sialization (1,2). In a healthy person, penta, tetra and trisial isoforms are detectible in plasma. However, in an alcohol abuse and/or dependence, asialo, monosialo and disialotransferrin isoforms are also present called carbohydrate-deficient transferrin (CDT) (3) . This is considered a specific biomarker of alcohol abusive and/or dependence, being useful in the diagnosis and monitoring of this pathology (4) . Aim: Verify compliance with the requirements of the manufacturer of the capillary electrophoresis method in laboratory practice and its suitability in determining the CDT. Materials and methods: The MiniCap System (Sebia) was used with calibrators traceable to the IFCC international reference procedure and normal and pathological internal control samples. Repeatability and intermediate precision tests were performed on control samples. From participation in External Quality Assessment (EQA) program (5 rounds - 2 samples each), Bias%, Deviation Index (DI) and Total Laboratory Error (TELab) were obtained. The Measurement Uncertainty was calculated by the Top Down Method (combined and expanded with a factor of 1.96), using the internal (CV%) and external (Bias%) quality control results. Results: In the repeatability tests, normal control samples (n=22, mean = 1.4%) were obtained, CV = 5.7%; for the pathological sample (n=24, mean = 5.4%), CV = 2.2%. In intermediate precision tests for the normal control sample, (n= 12, mean = 1.4%), CV = 6.7%; for the pathological sample (n=12, mean = 5.3%), CV = 4.9%. In samples from EQA program, mean Bias = -1.0% and TELab = 11.5. In the evaluation of the method by DI, 1 satisfactory, 7 good and 2 excellent results were obtained. The obtained Expanded Uncertainty (1.3% ± 0.3) is consistent with that indicated by the manufacturer. Conclusion: The TELab obtained meets Westgard`s desirable specifications (5) , being considered an appropriate methodology for use in laboratory practise for diagnosis. However, it is considered important to monitor the method with Internal Control samples, and participate in EQA programs, as well as periodic evaluation of Quality Indicators.

Keywords

Chronic Alcohol Abuse CDT - Carbohydrate-deficient Transferrin Alcohol Biomarker Capillary Electrophoresis Laboratory Quality Assessment Perturbações do Desenvolvimento Infantil e Saúde Mental