Reproducibility of serum oxysterols and lanosterol among postmenopausal women: Results from EPIC-Heidelberg.

BACKGROUND: Circulating oxysterols have been proposed as biological markers of disease risk. However, within-person reproducibility of circulating oxysterols over time is not well established.

METHODS: We evaluated the one-year reproducibility of 11 oxysterols and lanosterol among 30 postmenopausal women with repeat blood samples in the European Prospective Investigation into Cancer and Nutrition (EPIC) - Heidelberg, Germany cohort. Liquid chromatography-mass spectrometry (LC/MS) was performed to quantify serum concentrations of 22R-hydroxycholesterol, 25-hydroxycholesterol, 24S-hydroxycholesterol, 27-hydroxycholesterol, 22S-hydroxycholeterol, 24,25-epoxycholesterol, 5α,6β-dihydroxycholestanol, 7α-hydroxycholesterol, 5β,6β-epoxycholesterol, 5α,6α-epoxycholesterol, 24-dihydrolanosterol, and lanosterol. We evaluated Spearman correlations and intraclass correlation coefficients (ICCs) between quantifiable concentrations measured in repeat samples taken one-year apart to estimate within-person reproducibility.

RESULTS: Spearman correlations (ICCs) over one year ranged from 0 (ICC=0.10) for 5β,6β-epoxycholesterol and 0.10 (ICC=0.20) for 5α,6α-epoxycholesterol, representing low within-person stability, to 0.81 (ICC=0.75) for 27-hydroxycholesterol and 0.86 (ICC=0.91) for 24S-hydroxycholesterol, representing relatively high within-person stability. Correlations between oxysterols and lanosterol ranged from 0.01 between 24S-hydroxycholesterol and lanosterol to 0.70 between 5α,6α-epoxycholesterol and 5β,6β-epoxycholesterol.

CONCLUSIONS: Our results demonstrate that for 27-hydroxycholesterol, 24S-hydroxycholesterol, 25-hydroxycholesterol, 7α-hydroxycholesterol and lanosterol, a single serum measurement can reliably estimate average levels over a one-year period. Circulating oxysterols are of increasing interest in epidemiologic studies of chronic disease risk including cancer and cardiovascular disease. Our data suggest that within-person stability of oxysterols differs depending on the individual oxysterol evaluated. We identified four oxysterols and lanosterol as stable over time to inform the use of circulating oxysterols in epidemiologic studies.