title: Methionine/galactose ratio on newborn blood spots useful for reduction of false positives for homocystinuria and galactosemia by high-performance anion-exchange chromatography with pulsed amperometric detection.
abstract: BACKGROUND
  Methionine (Met) in blood and urine is a useful diagnostic marker for homocystinuria (HCU). However, galactosemia could be misdiagnosed as HCU when Met is used as the sole marker, since elevated excretion of Met presents in both galactosemia and HCU. Use of a more specific diagnostic marker in addition to Met is therefore necessary for reduction of false positive results for HCU as well as confirmative diagnosis of HCU.
  
  
  METHODS
  Chromatographic separation was performed using an anion-exchange column. The levels of Met and galactose (Gal) on blood were measured and Met/Gal ratios were calculated from blood spot samples from 300 normal volunteers, eight galactosemia patients, and three HCU patients.
  
  
  RESULTS
  The Met/Gal ratio ranged 0-4.95 for normal blood spots (n=300), 0-0.22 for galactosemia samples (n=8), and >1250 for HCU patient samples.
  
  
  CONCLUSIONS
  Separation, extraction, and deproteinization procedures were established for Met and Gal in blood spots. And Met/Gal ratio allowed HCU to clearly distinguish from galactosemia. As a way of second tier confirmative analysis, the ratio is the best way to reduce false positives. The assay is most appropriate to reduce false positives in labs that do not screen for galactosemia.
authors.affiliation: Department of Oriental Pharmaceutical Sciences, Kyung Hee East-West Pharmaceutical Research Institute, College of Pharmacy, Kyung Hee University, Seoul, South Korea.
authors.forename: Ji-Ye
authors.initials: JY
authors.lastname: Lee
authors.forename: Hee-Jung
authors.initials: HJ
authors.lastname: Sim
authors.forename: Ha-Jeong
authors.initials: HJ
authors.lastname: Kwon
authors.forename: Yong-Moon
authors.initials: YM
authors.lastname: Lee
authors.forename: Hye-Ran
authors.initials: HR
authors.lastname: Yoon
authors.forename: Seon-Pyo
authors.initials: SP
authors.lastname: Hong
mesh_terms: D000837:Anion Exchange Resins; D002851:Chromatography, High Pressure Liquid / Q000379:methods*; D002852:Chromatography, Ion Exchange / Q000379:methods*; D004563:Electrochemistry / Q000379:methods*; D005189:False Positive Reactions; D005690:Galactose / Q000097:blood*; D005693:Galactosemias / Q000097:blood / Q000175:diagnosis*; D006712:Homocystinuria / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D007231:Infant, Newborn; D008715:Methionine / Q000097:blood*; D015997:Neonatal Screening; D015203:Reproducibility of Results
chemical_list: D000837:Anion Exchange Resins; D008715:Methionine; D005690:Galactose