Differential effect of blood collection tubes on total free fatty acids (FFA) and total triiodothyronine (TT3) concentration: A model for studying interference from tube constituents

BackgroundBesides total triiodothyronine (TT3), total free fatty acids (FFA) concentrations were higher with serum separator tube (SST™) than Vacuette™ tubes.MethodsThe effects of surfactant, rubber stopper, and separator gel from various tubes were investigated on FFA, β-hydroxybutyrate (β-HB), and TT3 with 8 different tube types in blood specimens of apparently healthy volunteers.ResultsCompared to Vacuette tubes, serum FFA and TT3 concentrations were significantly higher in SST than glass tubes. Reformulated SST eliminated the increase in TT3 but not FFA. No significant difference was observed for β-HB concentration among tube types. Surfactant and rubber stoppers from the different tube types significantly increased TT3 but not FFA and β-HB concentrations. Agitation of whole blood but not serum or plasma specimens with separator gel from SST, reformulated SST and plasma preparation tube (PPT™) tubes compared to Vacuette tubes gave higher FFA but not β-HB levels.ConclusionsUnidentified component(s) from the separator gel in SST, reformulated SST and PPT tubes cause falsely high FFA concentration. In contrast to TT3, falsely high FFA results require exposure of whole blood and not serum to tube constituent(s). The approach employed here may serve as a model for assessing interference(s) from tube constituent(s).