TY - JOUR
T1 - Stability of 15 estrogens and estrogen metabolites in urine samples under processing and storage conditions typically used in epidemiologic studies
AU - Fuhrman, Barbara J.
AU - Xu, Xia
AU - Falk, Roni T.
AU - Hankinson, Susan E.
AU - Veenstra, Timothy D.
AU - Keefer, Larry K.
AU - Ziegler, Regina G.
PY - 2010/10
Y1 - 2010/10
N2 - Background: In preparation for large-scale epidemiologic studies of the role of estrogen metabolism in the etiology of breast and other cancers, we examined the stability of estrogens and estrogen metabolites (EM) in urine during processing and storage protocols. Methods: Fifteen EM were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in first morning urines from 3 premenopausal women. Linear regression was used to model log EM concentrations for each woman, with and without adding ascorbic acid (0.1% w/v), during storage at 4°C (7-8 time points, up to 48 hours), during long-term storage at -80°C (10 time points, up to 1 year), and by freeze-thaw cycles (up to 3). Results: Without ascorbic acid, concentrations (pmol/mL) of nearly all EM changed <1% per 24 hours of storage at 4°C, and <1% during storage at -80°C for 1 year; similarly, thawing and refreezing samples 3 times was not consistently associated with losses for any EM. Ascorbic acid had no clear beneficial effect on EM stability in these experiments. Conclusions: Given the large inter-individual variability in urinary EM concentrations, changes of the magnitude observed here are unlikely to cause substantial misclassification. Furthermore, processing and storage conditions studied here are adequate for use in epidemiologic studies.
AB - Background: In preparation for large-scale epidemiologic studies of the role of estrogen metabolism in the etiology of breast and other cancers, we examined the stability of estrogens and estrogen metabolites (EM) in urine during processing and storage protocols. Methods: Fifteen EM were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) in first morning urines from 3 premenopausal women. Linear regression was used to model log EM concentrations for each woman, with and without adding ascorbic acid (0.1% w/v), during storage at 4°C (7-8 time points, up to 48 hours), during long-term storage at -80°C (10 time points, up to 1 year), and by freeze-thaw cycles (up to 3). Results: Without ascorbic acid, concentrations (pmol/mL) of nearly all EM changed <1% per 24 hours of storage at 4°C, and <1% during storage at -80°C for 1 year; similarly, thawing and refreezing samples 3 times was not consistently associated with losses for any EM. Ascorbic acid had no clear beneficial effect on EM stability in these experiments. Conclusions: Given the large inter-individual variability in urinary EM concentrations, changes of the magnitude observed here are unlikely to cause substantial misclassification. Furthermore, processing and storage conditions studied here are adequate for use in epidemiologic studies.
KW - Estradiol
KW - Estrogen metabolites
KW - Estrogens
KW - Stability
KW - Urine
UR - http://www.scopus.com/inward/record.url?scp=78650818486&partnerID=8YFLogxK
U2 - 10.5301/JBM.2010.6086
DO - 10.5301/JBM.2010.6086
M3 - Article
C2 - 21161939
AN - SCOPUS:78650818486
SN - 0393-6155
VL - 25
SP - 185
EP - 194
JO - International Journal of Biological Markers
JF - International Journal of Biological Markers
IS - 4
ER -