False-Positive Meconium Test Results for Fatty Acid Ethyl Esters Secondary to Delayed Sample Collection

Authors

  • Irene Zelner,

    1. Division of Clinical Pharmacology & Toxicology, The Hospital for Sick Children, Toronto, Ontario, Canada
    2. Department of Pharmacology & Toxicology, University of Toronto, Toronto, Ontario, Canada
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  • Janine R. Hutson,

    1. Division of Clinical Pharmacology & Toxicology, The Hospital for Sick Children, Toronto, Ontario, Canada
    2. Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
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  • Bhushan M. Kapur,

    1. Division of Clinical Pharmacology & Toxicology, The Hospital for Sick Children, Toronto, Ontario, Canada
    2. Department of Clinical Pathology, Sunnybrook Health Science Center, Toronto, Ontario, Canada
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  • Denice S. Feig,

    1. Division of Endocrinology, Department of Medicine, Mount Sinai Hospital, University of Toronto, Toronto, Ontario, Canada;
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  • Gideon Koren

    Corresponding author
    1. Department of Pharmacology & Toxicology, University of Toronto, Toronto, Ontario, Canada
    2. Institute of Medical Sciences, University of Toronto, Toronto, Ontario, Canada
    3. Department of Medicine, University of Western Ontario, London, Ontario, Canada
    • Division of Clinical Pharmacology & Toxicology, The Hospital for Sick Children, Toronto, Ontario, Canada
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Reprint requests: Gideon Koren, MD, Division of Clinical Pharmacology and Toxicology, The Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada; Tel.: 416-813-5781; Fax: 416-813-7562; E-mail: gkoren@sickkids.ca

Abstract

Background

Meconium analysis for fatty acid ethyl esters (FAEEs) is a validated method for identifying heavy prenatal ethanol (EtOH) exposure. This study investigated whether delayed sample collection can result in false-positive test results for FAEEs because of collection of samples potentially contaminated with postnatally produced stool.

Methods

Serial excretions were prospectively collected from neonates born to nondrinking mothers to capture the transition from meconium to postnatal stool. These were analyzed for FAEEs using headspace-solid phase microextraction and gas chromatography–mass spectrometry. Experiments involving incubation of samples with glucose or EtOH were performed to explore a potential mechanism of FAEE elevation.

Results

A total of 136 samples were collected from 30 neonates during their first few days of life (median of 4 samples/baby over a mean period of 68.5 hours postpartum). Although the first-collected meconium sample tested negative for FAEEs in all babies, later samples tested above the 2 nmol/g positive cutoff in 19 of 30 babies. Median time to appearance of FAEE-positive samples was 59.2 hours postpartum. In vitro experiments demonstrated that FAEE levels can be further increased in late samples (likely containing postnatal stool) after incubation with glucose, and that FAEEs are readily formed in meconium in the presence of EtOH.

Conclusions

Collection of samples excreted later in the postpartum period can lead to false-positive test results for FAEEs, which could be because of contamination with dietary components of postnatally produced stool and EtOH-producing microorganisms. Clinically, it is critical to collect the earliest possible excretion for determination of FAEEs to ensure that the FAEE content is representative of in utero EtOH exposure.

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