Screening for serum total homocysteine in newborn children.
BACKGROUND
Newborn screening for total homocysteine (tHcy) in blood may identify babies with vitamin B12 (B12) deficiency or homocystinuria, but data on the causes of increased tHcy in screening samples are sparse.


METHODS
Serum concentrations of tHcy, cystathionine, methionine, folate, and B12 and the methylenetetrahydrofolate reductase (MTHFR) 677C > T polymorphism were determined in 4992 capillary blood samples collected as part of the routine screening program in newborn children. Methylmalonic acid (MMA), gender (SRY genotyping), and the frequency of six cystathionine beta-synthase (CBS) mutations were determined in 20-27% of the samples, including all samples with tHcy > 15 micromol/L (n = 127), B12 < 100 pmol/L (n = 159), or methionine > 40 micromol/L (n = 154).


RESULTS
The median (5th-95th percentile) tHcy concentration was 6.8 (4.2-12.8) micromol/L. B12 status, as determined by serum concentrations of B12, tHcy, and MMA, was moderately better in boys than in girls. tHcy concentrations between 10 and 20 micromol/L were often associated with low B12, whereas tHcy > 20 micromol/L (n = 43) was nearly always explained by increased methionine. tHcy did not differ according to folate concentrations or MTHFR 677C > T genotypes. None of the babies had definite CBS deficiencies, but heterozygosity led to low cystathionine, increased methionine, but normal tHcy concentrations.


CONCLUSIONS
Increased tHcy is a common but not specific finding in newborns. The metabolite and vitamin profiles will point to the cause of hyperhomocysteinemia. Screening for tHcy and related factors should be further evaluated in regions with high prevalence of homocystinuria and in babies at high risk of B12 deficiency.
Refsum
Helga
H
Department of Pharmacology, University of Oxford, UK. helga.refsum@pharmacology.oxford.ac.uk
Grindflek
Anne W
AW
Ueland
Per M
PM
Fredriksen
Ase
A
Meyer
Klaus
K
Ulvik
Arve
A
Guttormsen
Anne B
AB
Iversen
Ole E
OE
Schneede
Jørn
J
Kase
Bengt F
BF
D001800:Blood Specimen Collection; D003541:Cystathionine beta-Synthase / Q000235:genetics; D005260:Female; D005492:Folic Acid / Q000097:blood; D006710:Homocysteine / Q000097:blood*; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics; D015997:Neonatal Screening / Q000379:methods*; D011110:Polymorphism, Genetic; D012016:Reference Values; D044967:Serum; D012737:Sex Factors; D013997:Time Factors; D014806:Vitamin B 12 Deficiency / Q000175:diagnosis
D006710:Homocysteine; D005492:Folic Acid; D042965:Methylenetetrahydrofolate Reductase (NADPH2); D003541:Cystathionine beta-Synthase