title: Towards newborn screening for ornithine transcarbamylase deficiency: fast non-chromatographic orotic acid quantification from dried blood spots by tandem mass spectrometry.
abstract: BACKGROUND
  Orotic acid (OA) is the key parameter in the detection of ornithine transcarbamylase deficiency (OTC-D). Inclusion of OA into newborn screening compatibility with existing analytical procedures is necessary.
  
  
  METHODS
  OA was eluted from dried blood spots with methanol containing deuterated [1,3-(15)N2] OA as internal standard. Quantification by tandem mass spectrometry was accomplished without chromatographic separation. Samples were measured in MRM mode for the masses m/z 155.1 → 111 for OA and 157.1 → 113 for d2 OA.
  
  
  RESULTS
  OA was determined in a wide range of concentrations with high precision, LOD and LOQ being 0.21 and 0.65 μmol/L, respectively. Values correlated well with those obtained after chromatography. Pretreatment of samples with HCl-butanol regularly used for acylcarnitine measurement did not significantly affect quantitative results. Inclusion of the new method into the standard newborn screening procedure did not alter the results for acylcarnitines or amino acids; the total time per analysis, however, was increased from 1.15 to 1.85 min. OA levels of 707 unaffected newborns ranged from 0.28 to 3.73 μmol/L. Five newborns with OTC-D showed concentrations of 89.7-211.1 μmol/L. In newborns with severe citrullinaemia we found values in the range of 4.99-127.7 μmol/L.
  
  
  CONCLUSIONS
  This new method can be used as a standalone measurement of OA but it can also easily be implemented into standard newborn screening techniques as a useful supplement. In this case the method allows detection of newborns with OTC deficiency without an extra analytical run.
authors.affiliation: Screening-Labor Hannover, Hannover, Germany; Department of Neuropediatrics, Children's Hospital, Ruhr University of Bochum, Bochum, Germany; Department of Clinical Chemistry, Hannover Medical School, Hannover, Germany. Electronic address: Janzen.Nils@mh-hannover.de.
authors.forename: Nils
authors.initials: N
authors.lastname: Janzen
authors.affiliation: Screening-Labor Hannover, Hannover, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Terhardt
authors.affiliation: Screening-Labor Hannover, Hannover, Germany.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Sander
authors.affiliation: Children's Hospital, Istanbul University, Istanbul Medical Faculty, Istanbul, Turkey.
authors.forename: Mübeccel
authors.initials: M
authors.lastname: Demirkol
authors.affiliation: Children's Hospital, Istanbul University, Istanbul Medical Faculty, Istanbul, Turkey.
authors.forename: Gülden
authors.initials: G
authors.lastname: Gökçay
authors.affiliation: Screening-Labor Hannover, Hannover, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Peter
authors.affiliation: Department of Neuropediatrics, Children's Hospital, Ruhr University of Bochum, Bochum, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lücke
authors.affiliation: Screening-Labor Hannover, Hannover, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Sander
authors.affiliation: Paediatric Metabolic Medicine, Clinic for Paediatric Kidney, Liver- and Metabolic Diseases, Hannover Medical School, Hannover, Germany.
authors.forename: Anibh M
authors.initials: AM
authors.lastname: Das
mesh_terms: D059788:Dried Blood Spot Testing; D006801:Humans; D007231:Infant, Newborn; D015997:Neonatal Screening / Q000379:methods*; D020163:Ornithine Carbamoyltransferase Deficiency Disease / Q000097:blood* / Q000175:diagnosis* / Q000378:metabolism; D009963:Orotic Acid / Q000097:blood*; D053719:Tandem Mass Spectrometry
chemical_list: D009963:Orotic Acid
keywords: Newborn screening of urea cycle defects; OTC deficiency in newborns; Orotic acid