NMR-based metabolomics has shown
considerable promise in disease
diagnosis and biomarker discovery because it allows one to nondestructively
identify and quantify large numbers of novel metabolite biomarkers
in both biofluids and tissues. Precise metabolite quantification is
a prerequisite to move any chemical biomarker or biomarker panel from
the lab to the clinic. Among the biofluids commonly used for disease
diagnosis and prognosis, urine has several advantages. It is abundant,
sterile, and easily obtained, needs little sample preparation, and
does not require invasive medical procedures for collection. Furthermore,
urine captures and concentrates many “unwanted” or “undesirable”
compounds throughout the body, providing a rich source of potentially
useful disease biomarkers; however, incredible variation in urine
chemical concentrations makes analysis of urine and identification
of useful urinary biomarkers by NMR challenging. We discuss a number
of the most significant issues regarding NMR-based urinary metabolomics
with specific emphasis on metabolite quantification for disease biomarker
applications and propose data collection and instrumental recommendations
regarding NMR pulse sequences, acceptable acquisition parameter ranges,
relaxation effects on quantitation, proper handling of instrumental
differences, sample preparation, and biomarker assessment.