Reproducibility over 5 Years of Measurements of 6-Sulphatoxymelatonin in Urine Samples from Postmenopausal Women
- Cancer Research UK, Epidemiology Unit, University of Oxford, Oxford OX2 6HE, United Kingdom [R. C. T., N. E. A., T. J. K.], and Julius Center for Health Sciences and Primary Care, University Medical Center, Utrecht, 3508 GA Ultrecht, the Netherlands [P. H. M. P., P. A. H. v. N.]
Abstract
To assess the appropriateness of a single measurement of urinary 6-sulfatoxymelatonin (aMT6S) as a marker for long-term exposure to endogenous melatonin in epidemiological studies, we examined the reproducibility of aMT6S in first morning urine voids collected from 40 postmenopausal women. Urine specimens were collected on three different occasions, and the mean time between the first and the third urine sample was 5.1 years. Urinary aMT6S levels were measured by radioimmunoassay and adjusted for creatinine. The intraclass correlation for aMT6S adjusted for creatinine was 0.56 (95% confidence interval, 0.39–0.73). The classification of aMT6S concentrations in first morning voids from postmenopausal women appears to be sufficiently reproducible to justify its use as a marker for long-term exposure to melatonin in epidemiological studies.
Footnotes
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵1 To whom requests for reprints should be addressed, at Cancer Research UK, Epidemiology Unit, University of Oxford, Oxford OX2 6HE, United Kingdom. Phone: 01865-302234; Fax: 01865-310545; E-mail: ruth.travis{at}cancer.org.uk
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↵2 The abbreviations used are: melatonin, N-acetyl-5-methoxytryptamine; aMT6S, 6-sulfatoxymelatonin; DOM, Diagnostisch Onderzoek Mammacarcinoom; BMI, body mass index; ICC, intraclass correlation coefficient.
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- Accepted May 6, 1903.
- Received December 30, 1902.
- Revision received April 4, 1903.
