TY - JOUR
T1 - Analysis of guanidinoacetate and creatine by isotope dilution electrospray tandem mass spectrometry
AU - Bodamer, Olaf A.
AU - Bloesch, Shannon M.
AU - Gregg, Anthony R.
AU - Stockler-Ipsiroglu, Silvia
AU - O'Brien, William E.
PY - 2001/6/26
Y1 - 2001/6/26
N2 - Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine metabolism characterized by low plasma creatine concentrations in combination with elevated guanidinoacetate (GAA) concentrations. Although rare, GAMT deficiency has been identified in children with seizures, extrapyramidal movements, developmental delay, myopathies and behavioral abnormalities. Treatment with creatine monohydrate has been proven to be effective. We describe an isotope dilution electrospray tandem mass spectrometry (ES-MS/MS) assay for the simultaneous determination of plasma GAA and creatine using multiple reaction monitoring (MRM), d3-creatine as the internal standard and derivatization of GAA and creatine as butyl-esters. We analysed plasma of 16 healthy adults and 20 healthy children as well as three affected children. Plasma GAA concentrations were 5.02 ± 1.84 μmol/l (mean ± S.D.) in adults, 3.91 ± 0.76 μmol/l in children age 5-10 years and 11.57, 15.16, 14.36 μmol/l in children with GAMT deficiency. Plasma creatine concentrations were 34.7 ± 15.25 μmol/l in adults, 58.96 ± 22.30 μmol/l in children and 5.37, 8.15, 403.5 μmol/l in two untreated children and one treated child with GAMT deficiency, respectively. GAA can also be reliably measured from filter cards, which is sufficient to make the correct diagnosis while creatine is consistently falsely elevated probably secondary to liberation of red cell creatine. In nine healthy newborn infants, GAA concentrations from filter cards were 4.83 ± 1.43 and 5.04 ± 1.84 μmol/l in 16 healthy adults. We conclude that isotope dilution ES-MS/MS is ideal for rapid high-throughput diagnosis of GAMT deficiency both from plasma and filter paper cards. Using this technique neonatal screening is feasible for this treatable inborn error of creatine metabolism.
AB - Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine metabolism characterized by low plasma creatine concentrations in combination with elevated guanidinoacetate (GAA) concentrations. Although rare, GAMT deficiency has been identified in children with seizures, extrapyramidal movements, developmental delay, myopathies and behavioral abnormalities. Treatment with creatine monohydrate has been proven to be effective. We describe an isotope dilution electrospray tandem mass spectrometry (ES-MS/MS) assay for the simultaneous determination of plasma GAA and creatine using multiple reaction monitoring (MRM), d3-creatine as the internal standard and derivatization of GAA and creatine as butyl-esters. We analysed plasma of 16 healthy adults and 20 healthy children as well as three affected children. Plasma GAA concentrations were 5.02 ± 1.84 μmol/l (mean ± S.D.) in adults, 3.91 ± 0.76 μmol/l in children age 5-10 years and 11.57, 15.16, 14.36 μmol/l in children with GAMT deficiency. Plasma creatine concentrations were 34.7 ± 15.25 μmol/l in adults, 58.96 ± 22.30 μmol/l in children and 5.37, 8.15, 403.5 μmol/l in two untreated children and one treated child with GAMT deficiency, respectively. GAA can also be reliably measured from filter cards, which is sufficient to make the correct diagnosis while creatine is consistently falsely elevated probably secondary to liberation of red cell creatine. In nine healthy newborn infants, GAA concentrations from filter cards were 4.83 ± 1.43 and 5.04 ± 1.84 μmol/l in 16 healthy adults. We conclude that isotope dilution ES-MS/MS is ideal for rapid high-throughput diagnosis of GAMT deficiency both from plasma and filter paper cards. Using this technique neonatal screening is feasible for this treatable inborn error of creatine metabolism.
KW - Creatine
KW - Guanidinoacetate
KW - Guanidinoacetate methyltransferase
KW - Isotope dilution
KW - Neonatal screening
UR - http://www.scopus.com/inward/record.url?scp=0034971857&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0034971857&partnerID=8YFLogxK
U2 - 10.1016/S0009-8981(01)00480-6
DO - 10.1016/S0009-8981(01)00480-6
M3 - Article
C2 - 11412830
AN - SCOPUS:0034971857
VL - 308
SP - 173
EP - 178
JO - Clinica Chimica Acta
JF - Clinica Chimica Acta
SN - 0009-8981
IS - 1-2
ER -