The Effect of 3.2% and 3.8% Sodium Citrate on Specialized Coagulation Tests

Abstract

Context.— Coagulation testing is challenging and depends on preanalytic factors, including the citrate buffer concentration used. Objective.— To better estimate preanalytic effects of the citrate buffer concentration in use, the difference between results obtained by samples with 3.2% and 3.8% citrate was evaluated. Design.— In a prospective observational study with 76 volunteers, differences related to the citrate concentration were evaluated. For both buffer concentrations, reference range intervals were established according to the recommendations of the C28-A3 guideline published by the Clinical and Laboratory Standards Institute. Results.— In our reagent-analyzer settings, most parameters evaluated presented good comparability between citrated samples taken with 3.2% and 3.8% trisodium buffer. The ellagic acid containing activated partial thromboplastin time reagent (aPTT-FS) indicated a systemic and proportional difference between both buffer concentrations, leading to an alteration in its reference ranges. Further, a confirmation test for lupus anticoagulant assessment (Staclot LA) showed only a moderate correlation (rρ = 0.511) with a proportional deviation between both citrate concentrations. Further, a statistically significant difference was found in the diluted Russell viper venom time confirmation testing, coagulation factors V and VIII, and the protein C activity, which was found to be of minor clinical relevance. Conclusions.— With caution regarding the potential impact of the reagent-analyzer combination, our findings demonstrate the comparability of data assessed with 3.2% and 3.8% buffered citrated plasma. As an exception, the aPTT-FS and the Staclot LA assay were considerably affected by the citrate concentration used. Further studies are required to confirm our finding using different reagent-analyzer combinations.