Abstract
Background Besides total triiodothyronine (TT 3), total free fatty acids (FFA) concentrations were higher with serum separator tube (SST™) than Vacuette™ tubes. Methods The effects of surfactant, rubber stopper, and separator gel from various tubes were investigated on FFA, β-hydroxybutyrate (β-HB), and TT 3 with 8 different tube types in blood specimens of apparently healthy volunteers. Results Compared to Vacuette tubes, serum FFA and TT 3 concentrations were significantly higher in SST than glass tubes. Reformulated SST eliminated the increase in TT 3 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 TT 3 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. Conclusions Unidentified component(s) from the separator gel in SST, reformulated SST and PPT tubes cause falsely high FFA concentration. In contrast to TT 3, 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).
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