title: A novel method for simultaneous quantification of alpha-aminoadipic semialdehyde/piperideine-6-carboxylate and pipecolic acid in plasma and urine.
abstract: OBJECTIVE
  Elevated levels of pipecolic acid (PA), α-aminoadipic semialdehyde (AASA) and its cyclic form Δ1-piperideine-6-carboxylate (P6C) are characteristic of pyridoxine dependent epilepsy (PDE), a rare disorder of inborn error of metabolism. Recent studies showed the effectiveness of dietary therapy in PDE patients and emphasized the importance of the assessment of these metabolites for monitoring treatment efficacy. The objective of this study was to develop a robust and sensitive method for simultaneous quantification of AASA-P6C and PA in plasma and urine.
  
  
  METHODS
  Plasma and urine samples were derivatized with 3N HCl in n-butanol (v/v) and injected onto ACQUITY BEH-C18 column. A gradient of water/methanol containing 0.1% formic acid was used for the chromatographic separation of AASA, P6C and PA. The analytes' concentrations were calculated using their calibration curves and the sum of AASA and P6C (AASA-P6C) was calculated. To evaluate the clinical utility of this test, samples from unaffected controls and patients with confirmed PDE were analyzed.
  
  
  RESULTS
  The performance characteristics of the assay as well as sample stability and interferences were determined. The intra- and inter- assay CVs were ≤2.9% and ≤10.9% for AASA-P6C, and ≤3.3% and ≤12.6% for PA, respectively. Reference ranges for AASA-P6C and PA in plasma and urine were established. Comparison of values obtained from unaffected controls and PDE patients showed high clinical sensitivity and specificity of the assay.
  
  
  CONCLUSIONS
  This novel method for the simultaneous quantification of AASA-P6C and PA in plasma and urine can be used in a clinical laboratory setting for the diagnosis and monitoring of patients with PDE.
authors.affiliation: Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA. Electronic address: tatiana.n.yuzyuk@aruplab.com.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Yuzyuk
authors.affiliation: ARUP Laboratories, ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA.
authors.forename: Aiping
authors.initials: A
authors.lastname: Liu
authors.affiliation: Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA.
authors.forename: Amanda
authors.initials: A
authors.lastname: Thomas
authors.affiliation: Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA; Quest Diagnostics Nichols Institute, Chantilly, Virginia, USA.
authors.forename: JoDell E
authors.initials: JE
authors.lastname: Wilson
authors.affiliation: Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA.
authors.forename: Irene
authors.initials: I
authors.lastname: De Biase
authors.affiliation: Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA.
authors.forename: Nicola
authors.initials: N
authors.lastname: Longo
authors.affiliation: Department of Pathology, University of Utah, Salt Lake City, UT, USA; ARUP Laboratories, ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT, USA.
authors.forename: Marzia
authors.initials: M
authors.lastname: Pasquali
mesh_terms: D015074:2-Aminoadipic Acid / Q000737:chemistry*; D000447:Aldehydes / Q000737:chemistry*; D006801:Humans; D010848:Picolinic Acids / Q000032:analysis* / Q000097:blood / Q000652:urine; D010875:Pipecolic Acids / Q000032:analysis* / Q000097:blood / Q000652:urine; D012015:Reference Standards; D053719:Tandem Mass Spectrometry
chemical_list: D000447:Aldehydes; D010848:Picolinic Acids; D010875:Pipecolic Acids; D015074:2-Aminoadipic Acid; C008919:delta-1-piperidine-6-carboxylic acid
keywords: 1-piperideine-6-carboxylate; Alpha-aminoadipic semialdehyde; Pipecolic acid; Pyridoxine dependent epilepsy; UPLC–MS/MS