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Published on: June 25, 2010
A newborn screening method for cerebrotendinous xanthomatosis using bile alcohol glucuronides and metabolite ratios
Frédéric M Vaz1, Albert H Bootsma2, Willem Kulik2
1Department of Clinical Chemistry and Pediatrics, Laboratory of Genetic Metabolic Diseases, Academic Medical Center, Amsterdam, The Netherlands f.m.vaz@amc.nl.
Insights
Newborn screening for Cerebrotendinous xanthomatosis (CTX) is possible using a novel dried blood spot assay. This assay measures ratios of specific bile acids, enabling early detection and prevention of this neurodegenerative disorder.
Area of Science:
- Biochemistry
- Genetics
- Metabolic Disorders
Background:
- Cerebrotendinous xanthomatosis (CTX) is a rare, treatable neurodegenerative disorder affecting bile acid synthesis.
- Early diagnosis and chenodeoxycholic acid supplementation can prevent CTX symptoms, highlighting its suitability for newborn screening.
Purpose of the Study:
- To develop a novel dried blood spot (DBS) screening assay for CTX.
- To identify reliable biomarkers for CTX detection in newborns.
Main Methods:
- A new DBS assay was developed using tandem mass spectrometry without derivatization.
- The assay measures ratios of cholestanetetrol glucuronide (tetrol) to specific bile acids like taurochenodeoxycholic acid (t-CDCA).
- Analysis involved methanol extraction, internal standard addition, concentration, and flow injection analysis.
Main Results:
- The assay successfully differentiated between CTX patients and controls, including Zellweger patients and newborns with cholestasis.
- The tetrol:t-CDCA ratio demonstrated excellent separation as a derived biomarker for CTX.
- A pilot study using 217 Guthrie cards validated the assay's proof-of-principle.
Conclusions:
- The developed DBS assay and the tetrol:t-CDCA ratio show significant potential for CTX screening in neonatal programs.
- Early detection through newborn screening can lead to timely treatment and prevention of CTX-related neurodegeneration.
Abstract:
Cerebrotendinous xanthomatosis (CTX) is a treatable neurodegenerative metabolic disorder of bile acid synthesis in which symptoms can be prevented if treatment with chenodeoxycholic acid supplementation is initiated early in life, making CTX an excellent candidate for newborn screening. We developed a new dried blood spot (DBS) screening assay for this disorder on the basis of different ratios between the accumulating cholestanetetrol glucuronide (tetrol) and specific bile acids/bile acid intermediates, without the need for derivatization. A quarter-inch DBS punch was extracted with methanol, internal standards were added, and after concentration the extract was injected into the tandem mass spectrometer using a 2 min flow injection analysis for which specific transitions were measured for cholestanetetrol glucuronide, taurochenodeoxycholic acid (t-CDCA), and taurotrihydroxycholestanoic acid (t-THCA). A proof-of-principle experiment was performed using 217 Guthrie cards from healthy term/preterm newborns, CTX patients, and Zellweger patients. Using two calculated biomarkers, tetrol:t-CDCA and t-THCA:tetrol, this straightforward method achieved an excellent separation between DBSs of CTX patients and those of controls, Zellweger patients, and newborns with cholestasis. The results of this small pilot study indicate that the tetrol:t-CDCA ratio is an excellent derived biomarker for CTX that has the potential to be used in neonatal screening programs.
