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USDTL Research

Phosphatidylethanol Test More Sensitive Than CDT Marker

Recent studies have indicated that the direct alcohol biomarker phosphatidylethanol (PEth) is superior to indirect markers like carbohydrate deficient transferrin (CDT). PEth is a pathological phospholipid formed in tissues only by the action of phospholipase D on phosphatidylcholine and ethanol. PEth in blood remains in the red cell membrane until it spontaneously hydrolyses or is oxidized by lipid peroxidation.

USDTL took part in Dr. Marques’ DUI and biomarkers research by re-analyzing 281 blood specimens that had been previously analyzed for PEth at Lund University using a less sensitive HPLC/Light Scattering detector (LC/ LCD). The LC/LCD has a limit of quantitation of 250 ng/mL of total PEth which represents 100 ng/mL of the specific isomer of PEth USDTL determines by LC/MS/MS. The USDTL method has a limit of quantitation of 20 ng/mL. As seen from the correlation chart, many specimens negative by LC/ LSD were positive by USDTL’s LC/MS/MS method. Overall, the methods showed amazing agreement with an r2 of 0.846.

Using LC/MS/MS methodology, PEth analysis can identify as little as one drink (12 grams EtOH) per day over a week’s period. As a direct biomarker, PEth is not subject to the numerous pathological conditions that can produce false positives for CDT. A CDT test can produce false-positive results for alcohol use when pathological conditions such as obstructive liver disease and liver cirrhosis, among others, are present. Also, improved test methods in PEth appear to have reduced the other issues related to gender and age. Because of the lack of false positives along with its high sensitivity for detecting alcohol consumption, researchers conclude that it’s the most sensitive and specific alcohol biomarker available.

~~~For these reasons, USDTL now offers PEth testing using blood samples to test for alcohol exposure. The CDT assay requires consumption of 60 grams of ethanol per day for 10 days to 14 days to produce a positive, while PEthStatSM only requires about one drink a day per week. Therefore, pairing PethStatSM with UrineStatSM EtG/EtS, offers a unique combination of alcohol biomarkers for added insurance for your drug testing program. Requested sample volume is 5 milliliters of blood, and results are available four days to seven days after the sample is received in the laboratory. Call 1-800-235- 2367 to order PEthStatSM collection materials or visit for more information.~~~

For these reasons, USDTL offers PEth testing using dried blood spot to test for alcohol exposure. PEth is a mid to long-term alcohol biomarker, and a positive result (measuring PEth species 16:0/18:1) is an indication of alcohol exposure during up to approximately the last 2-4 weeks prior to specimen collection. Unlike venipuncture, dried blood spot (DBS) collection is performed by the specimen donor and can be observed by any staff member after a short training session. No medical personnel is needed. The special DBS card design locks blood into the fabric and, once dry, creates a specimen collection that is not considered a biohazard. No special storage or shipping needed. PEth turnaround time is 2 days for a negative screen, 3-4 days for confirmatory testing.

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