A new strategy implementing mass spectrometry in the diagnosis of congenital disorders of N-glycosylation (CDG)

Bruno Casetta, Sabrina Malvagia, Silvia Funghini, Diego Martinelli, Carlo Dionisi-Vici, Rita Barone, Agata Fiumara, Maria Alice Donati, Renzo Guerrini, Giancarlo La Marca

Research output: Contribution to journalArticlepeer-review


Congenital disorders of N-glycosylation (CDG) are a large group of rare metabolic disorders caused by defects in the most common post-translational modification of proteins. CDGs are often difficult to diagnose as they are manifested with non-specific symptoms and signs. Analysis of serum transferrin (TRF) isoforms, as the classical procedure used to identify a CDG patient, enables to predict pathological steps in the N-linked glycosylation process. We devised a new strategy based on liquid chromatography-mass spectrometry (LC-MS) for the analysis of TRF isoforms by combining a simple and fast sample preparation with a specific chromatographic cleanup/separation step followed by mass-spectrometric measurement. Single TRF isoform masses were obtained through reconstruction of multiply charged electrospray data collected by quadrupole-MS technology. Hereby, we report the first analyzed serum samples obtained from 20 CDG patients and 100 controls. The ratio of desialylated isoforms to total TRF was calculated for patients and controls. CDG-Type I patients showed higher amounts of bi-sialo isoform (range: 6.7-29.6%) compared to controls (<5.5%, mean percentage 3.9%). CDG-Type II pattern showed an increased peak of tri-sialo isoforms. The mean percentage of tri-sialo-TRF was 9.3% (range: 2.9-12.9%) in controls, which was lower than that obtained from two patients with COG5-CDG and MAN1B1-CDG (18.5 and 24.5%). Intraday and between-day imprecisions were less than 9 and 16%, respectively, for bi-sialo- and less than 3 and 6% for tri-sialo-TRF. This LC-MS-based approach provides a simple, sensitive and fast analytical tool for characterizing CDG disorders in a routine clinical biochemistry while improving diagnostic accuracy and speeding clinical decision-making.

Original languageEnglish
Pages (from-to)165-171
Number of pages7
JournalClinical Chemistry and Laboratory Medicine
Issue number1
Publication statusPublished - 2020


  • congenital disorders of N-glycosylation (CDG)
  • inborn error of metabolism
  • liquid chromatography-mass spectrometry (LC-MS)
  • N-glycosylation
  • online trapping and clean-up
  • spectral deconvolution
  • transferrin isoforms

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Biochemistry, medical


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