Development and validation of an LC-MS/MS method for the simultaneous detection of urinary inflammatory biomarkers in a Flemish birth cohort.

Chronic inflammation is a significant contributor to various diseases but its assessment via blood sampling presents challenges, particularly in children. The evaluation of urinary biomarkers, including 3-bromotyrosine (Bty), 3-chlorotyrosine (Cty) and leukotriene E4 (LTE4), offers a non-invasive alternative. This study presents the optimization and validation of a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the simultaneous quantification of Bty, Cty and LTE4 in urine. Under optimized conditions, sample preparation was based on SPE using Oasis MAX cartridges, followed by LC-MS/MS analysis. Method performance was validated using the ICH 10 guidelines, resulting in satisfactory results for all analytes in terms of recovery, linearity, limits of quantification, precision and accuracy. Recovery rates ranged from 82 % to 97 %, while matrix effects were observed within the range of -11 % to 26 %. Linear range spanned from 0.08 to 20 ng/mL for the three analytes. Application to 332 urine samples from the ENVIRONAGE birth cohort (Belgium), comprising of children aged 4-11 years, revealed detection frequencies of 18 % for LTE4, 19 % for Cty and 50 % for Bty. Notably, creatinine-corrected Cty and LTE4 exhibited statistically significant Spearman correlations with established systemic inflammation markers. Specifically, Cty was positively correlated with absolute monocyte count (ρ = 0.53, p < 0.05), while LTE4 showed a positive correlation with relative eosinophil levels (ρ = 0.46, p < 0.05) and a negative correlation with the relative neutrophil levels (ρ = -0.56, p < 0.01). These results highlight the validated method as a valuable tool for investigating distinct inflammatory pathways in epidemiological settings and clinical research.