title: Identification and Characterization of EDTA Test Strip Interfering Substances Using a Digital Color Detector.
abstract: BACKGROUND
  Rapid test strips for ethylenediaminetetraacetic acid (EDTA) can be used to verify correct specimen types for clinical assays which require, or cannot be performed on, plasma collection tubes containing EDTA anticoagulant. As the test strip reaction chemistry is based on a color change induced by chelation of bismuth from a xylenol orange complex, we hypothesized that any agent capable of chelating bismuth might induce false positive test strip reactivity. The present study was therefore designed to evaluate the potential for test strip interference by chelating agents commonly used in the treatment of trace and heavy metal toxicity.
  
  
  METHODS
  A digital color detector mounted on a 3D-printed test strip holder was used to quantitatively assess test strip reactivity and evaluate concentration-response relationships of eight commercially available chelating agents.
  
  
  RESULTS
  This approach revealed the following rank-order potency: K2EDTA = Na2EDTA > ethylene glycol tetra-acetic acid (EGTA) > dimercaptosuccinic acid (DMSA) > 2,3-dimercapto-1-propanesulfonic acid (DMPS) > penicillamine (PEN). Both deferoxamine (DEF) and alpha lipoic acid (ALA) were non-reactive at 10 mM concentrations.
  
  
  CONCLUSIONS
  These experiments demonstrate that multiple substances can induce EDTA rapid test strip reactivity, but only at concentrations higher than might be expected during therapeutic chelation therapy. These agents are therefore unlikely to cause false positive results in routine clinical laboratory specimens.
authors: Kelly L
authors: KL
authors: Scholes
authors: Ammon T
authors: AT
authors: Ence
authors: Frederick G
authors: FG
authors: Strathmann
authors: Jonathan R
authors: JR
authors: Genzen
mesh_terms: D001729:Bismuth / Q000737:chemistry; D002614:Chelating Agents / Q000032:analysis* / Q000737:chemistry / Q000627:therapeutic use; D003124:Colorimetry / Q000295:instrumentation; D004492:Edetic Acid / Q000097:blood* / Q000737:chemistry / Q000627:therapeutic use; D004867:Equipment Design; D005189:False Positive Reactions; D000075322:Heavy Metal Poisoning; D006801:Humans; D011041:Poisoning / Q000188:drug therapy*; D011237:Predictive Value of Tests; D011934:Reagent Strips; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000379:methods*
chemical_list: D002614:Chelating Agents; D011934:Reagent Strips; D004492:Edetic Acid; D001729:Bismuth