title: Galactose-1-phosphate uridyltransferase dried blood spot quality control materials for newborn screening tests.
abstract: OBJECTIVE
  We aimed to prepare dried-blood-spot (DBS) quality control (QC) materials for galactose-1-phosphate uridyltransferase (GALT), to evaluate their stability during storage and use, and to evaluate their performance in five DBS GALT test methods.
  
  
  METHODS
  We prepared and characterized GALT-normal and GALT-deficient DBS materials and compared GALT activities in DBSs after predetermined storage intervals at controlled temperatures and humidities. External evaluators documented the suitability of the DBS QC materials for use in five GALT test methods.
  
  
  RESULTS
  GALT activity losses from DBSs stored in low (<30%) humidity for 14 days at 45°C, 35 days at 37°C, 91 days at room temperature, 182 days at 4°C, and 367 days at -20°C were 54%, 53%, 52% 23%, and 7% respectively. In paired DBSs stored in high humidity (>50%) for identical intervals, losses were: 45°C-68%; 37°C-79%; room temperature-72%, and 4°C-63%. GALT activities in DBSs stored at 4°C were stable throughout 19 excursions to room temperature. Twenty-five of 26 external evaluators, using five different GALT test methods, classified the GALT-deficient DBSs as "outside normal limits". All evaluators classified the GALT-normal DBSs as "within normal limits".
  
  
  CONCLUSIONS
  Most of the GALT activity loss from DBSs stored at elevated or room temperature was attributable to the effects of storage temperature. Most of the loss from DBSs stored at 4°C was attributable to the effects of elevated humidity. Loss from DBSs stored at -20°C was insignificant. The DBS materials were suitable for monitoring performance of all five GALT test methods.
authors.affiliation: Centers for Disease Control and Prevention (CDC), 4770 Buford Highway NE, Atlanta, GA 30341, USA. Electronic address: barbaraadam@att.net.
authors.forename: Barbara W
authors.initials: BW
authors.lastname: Adam
authors.affiliation: Centers for Disease Control and Prevention (CDC), 4770 Buford Highway NE, Atlanta, GA 30341, USA.
authors.forename: Sharon R
authors.initials: SR
authors.lastname: Flores
authors.affiliation: Genetic Disease Laboratory Branch, California Department of Public Health, 850 Marina Bay Pkwy, Richmond, CA 94804, USA.
authors.forename: Yu
authors.initials: Y
authors.lastname: Hou
authors.affiliation: Astoria-Pacific, Inc., 15130 SE 82nd Drive, P.O. Box 830, Clackamas, OR 97015, USA.
authors.forename: Todd W
authors.initials: TW
authors.lastname: Allen
authors.affiliation: Centers for Disease Control and Prevention (CDC), 4770 Buford Highway NE, Atlanta, GA 30341, USA.
authors.forename: Victor R
authors.initials: VR
authors.lastname: De Jesus
mesh_terms: D059788:Dried Blood Spot Testing; D057075:Enzyme Assays; D004795:Enzyme Stability; D005693:Galactosemias / Q000097:blood / Q000175:diagnosis* / Q000201:enzymology; D006801:Humans; D007231:Infant, Newborn; D015997:Neonatal Screening; D011309:Preservation, Biological; D011785:Quality Assurance, Health Care; D005694:UTP-Hexose-1-Phosphate Uridylyltransferase / Q000097:blood* / Q000737:chemistry
chemical_list: D005694:UTP-Hexose-1-Phosphate Uridylyltransferase
keywords: Blood spots; Galactose-1-phosphate uridyltransferase; Galactosemia; Newborn screening; Quality control; Sample integrity