Correcting for the influence of sampling conditions on biomarkers of exposure to phenols and phthalates: a 2-step standardization method based on regression residuals.

Marion Mortamais (1, 2) , Cécile Chevrier (3) , Claire Philippat (2) , Claire Petit (3) , Antonia M Calafat (4) , Xiaoyun Ye (4) , Manori J Silva (4) , Christian Brambilla (5) , Marinus J C Eijkemans (6) , Marie-Aline Charles (7) , Sylvaine Cordier (3) , Rémy Slama (2)

1 PSNREC - Neuropsychiatrie : recherche épidémiologique et clinique
2 INSERM U823 - Institut d'oncologie/développement Albert Bonniot de Grenoble
3 GERHM - Groupe d'Etude de la Reproduction Chez l'Homme et les Mammiferes
4 CDC - Centers for Disease Control and Prevention [Atlanta]
5 Groupe de Recherche Sur Le Cancer du Poumon : Bases Moléculaires de la Progression Tumorale, Dépistage et Thérapie Génique
6 Julius Center for Health Sciences and Primary Care
7 CESP - Centre de recherche en épidémiologie et santé des populations

BACKGROUND: Environmental epidemiology and biomonitoring studies typically rely on biological samples to assay the concentration of non-persistent exposure biomarkers. Between-participant variations in sampling conditions of these biological samples constitute a potential source of exposure misclassification. Few studies attempted to correct biomarker levels for this error. We aimed to assess the influence of sampling conditions on concentrations of urinary biomarkers of select phenols and phthalates, two widely-produced families of chemicals, and to standardize biomarker concentrations on sampling conditions. METHODS: Urine samples were collected between 2002 and 2006 among 287 pregnant women from Eden and Pélagie cohorts, from which phthalates and phenols metabolites levels were assayed. We applied a 2-step standardization method based on regression residuals. First, the influence of sampling conditions (including sampling hour, duration of storage before freezing) and of creatinine levels on biomarker concentrations were characterized using adjusted linear regression models. In the second step, the model estimates were used to remove the variability in biomarker concentrations due to sampling conditions and to standardize concentrations as if all samples had been collected under the same conditions (e.g., same hour of urine collection). RESULTS: Sampling hour was associated with concentrations of several exposure biomarkers. After standardization for sampling conditions, median concentrations differed by--38% for 2,5-dichlorophenol to +80 % for a metabolite of diisodecyl phthalate. However, at the individual level, standardized biomarker levels were strongly correlated (correlation coefficients above 0.80) with unstandardized measures. CONCLUSIONS: Sampling conditions, such as sampling hour, should be systematically collected in biomarker-based studies, in particular when the biomarker half-life is short. The 2-step standardization method based on regression residuals that we proposed in order to limit the impact of heterogeneity in sampling conditions could be further tested in studies describing levels of biomarkers or their influence on health.

Mots clés: Biomarker; Endocrine Disruptor; Phenols; Phthalate esters; Pregnancy; Sampling conditions

Domaines: Santé

Marion Mortamais, Cécile Chevrier, Claire Philippat, Claire Petit, Antonia M Calafat, et al.. Correcting for the influence of sampling conditions on biomarkers of exposure to phenols and phthalates: a 2-step standardization method based on regression residuals.. Environmental Health, 2012, 11, pp.29. ⟨10.1186/1476-069X-11-29⟩. ⟨hal-00875974⟩