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Clinical Chemistry 48: 604-612, 2002;
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(Clinical Chemistry. 2002;48:604-612.)
© 2002 American Association for Clinical Chemistry, Inc.

Erythrocyte Galactose 1-Phosphate Quantified by Isotope-Dilution Gas Chromatography-Mass Spectrometry

Jie Chen1, Claire Yager1, Robert Reynolds1, Michael Palmieri2 and Stanton Segal1,2,3a

1 Metabolic Research Laboratory and
2 Metabolic Diagnostic Laboratory, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104.

3 Department of Pediatrics, University of Pennsylvania School of Medicine, Philadelphia, PA 19104.

aAddress correspondence to this author at: Metabolic Research Laboratory, The Children’s Hospital of Philadelphia, Philadelphia, PA 19104. Fax 215-590-3364; e-mail segal{at}email.chop.edu.

Background: Measurements of {alpha}-D-galactose 1-phosphate (Gal-1-P) in erythrocytes are used to monitor the adequacy of dietary therapy in the treatment of galactosemia. We have devised a gas chromatography-mass spectrometry (GC/MS) isotope-dilution method for quantification of Gal-1-P.

Methods: We prepared trimethylsilyl (TMS) derivatives and used {alpha}-D-[2-13C]Gal-1-P as the internal standard for GC/MS. Results obtained with this method were compared with those determined by the established enzymatic method for samples from 23 healthy individuals (11 children and 12 adults), 9 suspected patients with galactosemia, 12 galactosemic patients on diet therapy, and 2 newly diagnosed toxic neonates.

Results: The method was linear up to 2.5 mmol/L with a lower limit of detection of 2.1 nmol (0.55 mg/L). Intra- and interassay imprecision (CVs) was 2.2–8.8%. In the 23 healthy individuals, values ranged from nondetectable to 9.2 µmol/L (2.4 mg/L of packed erythrocytes). Galactosemic patients on diet therapy had values of 10.9–45 mg/L of packed erythrocytes, whereas the newly identified patients had values of 166 and 373 mg/L.

Conclusions: The GC/MS method is precise and useful over the wide range of concentrations needed to assess the galactose burden in patients with galactosemia.






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Copyright © 2002 by the American Association for Clinical Chemistry.