Related Experiment Video
Updated: Aug 21, 2026
Hemocompatibility Testing of Blood-Contacting Implants in a Flow Loop Model Mimicking Human Blood Flow
Published on: March 5, 2020
Fluoride-Oxalate and Lithium Heparin Anticoagulant Tubes Are Reliable Alternatives to EDTA for HbA1c Measurement
Lamia Abdellaoui1, Asma Krir1, Manel Soltani1
1Department of Clinical Biochemistry, Pasteur Institute of Tunis, University of Tunis El Manar, Tunis, Tunisia, pasteur.tn.
Background:
The dual role of HbA1c in diagnosing and monitoring diabetes mellitus has driven a continuous increase in routine testing requests. To optimize laboratory workflows and avoid dedicated EDTA blood draws, this study is aimed at determining whether fluoride-oxalate and lithium heparin anticoagulant tubes could serve as reliable alternatives to EDTA tubes for HbA1c measurement on the COBAS INTEGRA 400 plus analyzer.
Methods:
Over 2 months at the Pasteur Institute of Tunis, paired blood samples from patients undergoing routine HbA1c testing were analyzed. Standard K3-EDTA tubes were compared with either lithium heparin or fluoride-oxalate tubes using a turbidimetric inhibition immunoassay on a COBAS INTEGRA 400 plus analyzer. The study relied exclusively on residual clinical material without imposing specific preanalytical restrictions.
Results:
The study population comprised 277 patients, divided into Group 1 (K3-EDTA vs. fluoride-oxalate, n = 200) and Group 2 (K3-EDTA vs. lithium heparin, n = 77). HbA1c results from both alternative tubes showed strong correlation with K3-EDTA (r = 0.99, p < 0.0001), with no significant overall differences. Passing-Bablok regression revealed no constant or proportional bias for lithium heparin, whereas a systematic bias was observed for fluoride-oxalate. Bland-Altman analysis of log-transformed data indicated no significant mean bias for either fluoride-oxalate (-0.15%; 95% LoA [-2.76% to +2.53%]) or lithium heparin (-0.04%; 95% LoA [-2.77% to +2.76%]), although a slight proportional bias was detected in both. Finally, HbA1c measurements in both tube types exhibited high diagnostic performance at clinical cutoffs (p < 0.0001).
Conclusions:
Fluoride-oxalate and lithium heparin anticoagulant tubes provide reliable alternatives to standard K3-EDTA tubes for HbA1c measurement, with no clinically meaningful differences observed. However, we emphasize that these results are strictly validated for the Roche COBAS immunoassay.
Related Concept Videos
01:23EDTA: Indirect and Alkalimetric Titration
01:18Effects of EDTA on End-Point Detection Methods
In the visual method, metal-ion indicators (metallochromic dyes), which have distinct colors in their free and complex forms, are added to the mixture to signal the titration's end point. They form stable complexes with metal ions, but these complexes are weaker than the corresponding metal–EDTA complexes. As a result, EDTA...
01:30EDTA: Direct, Back-, and Displacement Titration
Direct titration involves buffering the metal ion solution to the desired pH and directly titrating with standard EDTA until the endpoint. The optimum pH ensures a large conditional formation constant of metal−EDTA and visibility of the free indicator color in the solution. In addition, auxiliary complexing reagents are used to prevent the precipitation of metal hydroxides and...
01:22EDTA: Chemistry and Properties
01:26EDTA: Auxiliary Complexing Reagents
01:19Masking and Demasking Agents
There are many masking agents, such as cyanide, fluoride, triethanolamine, thiourea, and 2,3-bis(sulfanyl)propan-1-ol (formerly 2,3-dimercapto-1-propanol), with the masking agent chosen based on the metal...