title: Reference interval of methylmalonic acid concentrations in dried blood spots of healthy, term newborns to facilitate neonatal screening of vitamin B12 deficiency.
abstract: OBJECTIVE
  Unrecognized vitamin B12 (B-12) deficiency in early infancy can lead to poor development of the child. Methylmalonic acid (MMA) is the most specific functional biomarker of B-12 status. To facilitate timely diagnosis and treatment of neonatal B-12 deficiency, the objective of this study was to calculate a reference interval of MMA in dried blood spots (DBSs) of healthy, term newborns.
  
  
  METHODS
  MMA was quantified in 160 newborn DBSs, routinely collected for newborn screening, using LC-MS/MS. The reference interval of DBS MMA was calculated according to current guidelines (CLSI EP28-A3c). The effect of storage at room temperature on DBS MMA concentrations was determined.
  
  
  RESULTS
  The mean DBS MMA concentration of 160 healthy, term newborns was 16.8pmol (95% CI: 15.9-17.6pmol)/8-mm spot. The reference interval (2.5th to 97.5th percentile) for MMA was 9.89 to 29.3pmol/8-mm spot (0.450 to 1.33μmol/L whole blood). DBS MMA concentrations correlated positively (p<0.005) with storage time at room temperature. DBS MMA concentrations of children with methylmalonic acidemia (n=4) were above the upper limit of the reference interval.
  
  
  CONCLUSIONS
  This is the first study to present a reference interval for DBS MMA of healthy, term newborns utilizing a new highly sensitive MMA method. Analysis of DBS MMA collected during newborn screening may have the potential to identify newborns with acquired B-12 deficiency. Newborn DBS MMA concentrations increase with storage at room temperature, therefore, sample storage has to be monitored for evaluation of DBS MMA data.
authors.affiliation: Food, Nutrition and Health, Faculty of Land and Food Systems, The University of British Columbia, 2205 East Mall, Vancouver, BC V6T 1Z4, Canada; Child and Family Research Institute, 950 W 28th Ave, Vancouver, BC V5Z 4H4, Canada. Electronic address: schrod10@mail.ubc.ca.
authors.forename: Theresa H
authors.initials: TH
authors.lastname: Schroder
authors.affiliation: Child and Family Research Institute, 950 W 28th Ave, Vancouver, BC V5Z 4H4, Canada; Department of Clinical Chemistry and Laboratory Medicine, The University of British Columbia; St Paul's Hospital, 1081 Burrard St, Vancouver, BC V6Z 1Y6, Canada. Electronic address: amattman@providencehealth.bc.ca.
authors.forename: Andre
authors.initials: A
authors.lastname: Mattman
authors.affiliation: Child and Family Research Institute, 950 W 28th Ave, Vancouver, BC V5Z 4H4, Canada; Department of Pathology and Laboratory Medicine, The University of British Columbia; BC Children's Hospital and BC Women's Health Centre, 4480 Oak Street, Vancouver, BC V6H 3V4, Canada. Electronic address: gsinclair@cw.bc.ca.
authors.forename: Graham
authors.initials: G
authors.lastname: Sinclair
authors.affiliation: Child and Family Research Institute, 950 W 28th Ave, Vancouver, BC V5Z 4H4, Canada; Department of Pathology and Laboratory Medicine, The University of British Columbia; BC Children's Hospital and BC Women's Health Centre, 4480 Oak Street, Vancouver, BC V6H 3V4, Canada. Electronic address: hvallance@cw.bc.ca.
authors.forename: Hilary D
authors.initials: HD
authors.lastname: Vallance
authors.affiliation: Food, Nutrition and Health, Faculty of Land and Food Systems, The University of British Columbia, 2205 East Mall, Vancouver, BC V6T 1Z4, Canada; Child and Family Research Institute, 950 W 28th Ave, Vancouver, BC V5Z 4H4, Canada. Electronic address: yvonne.lamers@ubc.ca.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Lamers
mesh_terms: D006801:Humans; D007231:Infant, Newborn; D007232:Infant, Newborn, Diseases / Q000097:blood / Q000175:diagnosis*; D008764:Methylmalonic Acid / Q000097:blood*; D015997:Neonatal Screening; D012016:Reference Values; D014806:Vitamin B 12 Deficiency / Q000097:blood / Q000175:diagnosis*
chemical_list: D008764:Methylmalonic Acid
keywords: Deficiency; Dried blood spots; Liquid chromatography–tandem mass spectrometry; Methylmalonic acid; Methylmalonic acidemia; Newborn screening; Newborns; Reference interval; Vitamin B-12