Evaluation of Test Strips for the Rapid Identification of Ethylenediaminetetraacetic Acid (EDTA) Specimens

Background: Identification of specimens that contain ethylenediaminetetraacetic acid (EDTA) is frequently necessary when investigating potentially mislabeled or improperly collected specimens. Objective: To evaluate the performance of rapid EDTA detection test strips in clinical specimens. Methods: We applied specimens to test strips designed to detect EDTA (QUANTOFIX EDTA) using a pipet ( drop mode ). Reactions were scored visually on a scale from red (no EDTA) to orange (low/indeterminate EDTA) to yellow (contains EDTA). Results: Test strips reliably identified specimens from EDTA-containing tube types. Although test strips did not detect strong reactivity in other specimens, tubes containing NaFl/K-oxalate produced an orange (low/indeterminate EDTA) reaction. Bismuth and citrate levels were higher in specimens after we dipped test strips into solution ( dip mode) . Conclusions: Test strips detected the presence of EDTA in concentrations found in EDTA-containing primary tubes. Test strips were less effective in evaluating low-level EDTA concentrations expected with intravenous line contamination or backflow. Indeterminate reactions required further investigation. Dip mode can produce analytical problems for assays that measure (or are interfered by) the contents of test strips. * EDTA : ethylenediaminetetraacetic acid NaB : sodium tetraphenylborate IRB : institutional review board NaFl : sodium fluoride BD : Becton Dickinson and Co. ACD : acid citrate dextrose ddH2O : demineralized distilled water Bi : bismuth BoCS : bovine calf serum HIL : hemolysis icterus lipemia RBCs : red blood cells PBS : phosphate-buffered saline ICP-MS : inductively coupled plasma-mass spectrometry BAPTA : bis–ethane-N,N,N′,N′-tetraacetic acid PPE : personal protective equipment Y : yellow O : orange R : red PST : plasma separator tube SST : serum separator tube RST : rapid serum tube