The application of metabolic phenotyping in clinical and
epidemiological studies is limited by a poor understanding of
inter-individual, intra-individual and temporal variability in
metabolic phenotypes. Using 1H NMR spectroscopy we characterised
short-term variability in urinary metabolites measured from 20
children aged 8-9 years old. Daily spot morning, night-time and
pooled (50:50 morning and night-time) urine samples across six
days (18 samples per child) were analysed, and 44 metabolites
quantified. Intraclass correlation coefficients (ICC) and mixed
effect models were applied to assess the reproducibility and
biological variance of metabolic phenotypes. Excellent
analytical reproducibility and precision was demonstrated for
the 1H NMR spectroscopic platform (median CV 7.2%). Pooled
samples captured the best inter-individual variability with an
ICC of 0.40 (median). Trimethylamine, N-acetyl neuraminic acid,
3-hydroxyisobutyrate, 3-hydroxybutyrate/3-aminoisobutyrate,
tyrosine, valine and 3-hydroxyisovalerate exhibited the highest
stability with over 50% of variance specific to the child. The
pooled sample was shown to capture the most inter-individual
variance in the metabolic phenotype, which is of importance for
molecular epidemiology study design. A substantial proportion of
the variation in the urinary metabolome of children is specific
to the individual, underlining the potential of such data to
inform clinical and exposome studies conducted early in life