Chapter 21 - Mass spectrometry in clinical treatment

Abstract

This chapter focuses on the clinical use of mass spectrometry (MS) in pediatrics and oncology. Mass spectrometry (MS) is widely used for newborn screening. In diagnoses of some rare conditions, such as bile acid synthetic defects, MS can also be utilized. Nowadays it is possible to screen and rapidly diagnose potential or real inborn errors in bile acid synthesis from urinary bile acid analysis by means of MS. Specific mutations in the genes that encode the enzymes responsible for bile acid synthesis can be identified by molecular techniques. Stable-isotope-labeled reference compounds are used as internal standards to determine uracil and thymine as well as their degradation products in urine by means of reversed-phase HPLC coupled with electrospray ionization MS/MS. MS can also be used for optimizing cancer therapy. A method for the quantification of plasma 2'-deoxyuridine (UdR) has been developed and validated. Only 1 ml plasma is required, which is subjected to a clean-up step with anion-exchange solid-phase extraction followed by HPLC separation and atmospheric pressure CI-MS detection in a selected-ion monitoring mode. The method has the sensitivity, precision, accuracy, and selectivity required for routine analysis, the limit of quantitation being 5 nmol/l, which is certainly sufficient for clinical studies.