Forensic Drug Testing Lab
Dried Blood Spots
Dried blood spot collection is the fastest, most convenient way to test for phosphatidylethanol (PEth)Phosphatidylethanol (PEth)PEth is created in red blood cells where it exists as part of the cell membrane. Research suggests a PEth test can differentiate between incidental exposure (hand sanitizer use, etc.) and the intentional use of ethanol. A PEth test in blood gives a 2-3 week history of alcohol (ab)use. We offer PEth testing in both dried blood spots and whole blood. The sample amount is 5 dried blood spots from a finger puncture or 5 ml of blood from a standard blood draw using anticoagulation tube collection.. Standard collection supplies provided include 2 lancets, 2 alcohol prep pads, gauze, a collection card, and the dried blood spot drying box. We also provide the requisition form for the collection, which includes all necessary bar code stickers to maintain a proper chain-of-custody. Unlike venipuncture, dried blood spot collection is performed by the individual being tested (the donor) and can be observed by any staff member, after a short training session. The dried blood spot drying box makes collection even easier by eliminating wait time. PEth is an abnormal phospholipid formed in red blood cells following alcohol exposure. PEth in blood exists as a component of the red cell membrane. PEth is a mid to long-term alcohol biomarker, and a positive result (measuring phosphatidylethanol species 16:0/18:1) is an indication of alcohol exposure during the 2-3 weeks prior to sample collection.
Click here to view dried blood spot collection instructions.
Click here to view dried blood spot collection slides.
Whole Blood Specimens
For those interested in whole blood testing, we test for THC, EtOH, and PEth.
Click here to view whole blood collection instructions.
Click here to view the PEth Resources page.
*Click the green and white plus sign beside each drug class to view the substances within each class.
CAUTION: Do not use an ethanol-based sanitizer.
passport) and record the donor information in Step 1 of the requisition form.
By Phone: 1.800.235.2367
Business Hours (CST)
Monday 6am - 8pm
Tuesday 6am - 8pm
Wednesday 6am - 8pm
Thursday 6am - 8pm
Friday 6am - 8pm
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Can we use any tube for whole blood collection?
Please use only purple, gray, and green top tubes.
Do we need to spin (centrifuge) whole blood samples?
How do PEth results differ from Urine EtG/EtS results?
How much blood is required for a PEth testing sample?
5 individual large drops on a collection card.
How much blood is required for whole blood testing?
Requested sample volume is 5 milliliters.
What is the window of detection for PEth?
What is the window of detection for whole blood testing?
Whole blood testing for substances of abuse identifies usage over a 2-3 day period.
When will I receive whole blood testing results?
Which phosphatidylethanol species do you measure during PEth testing?
Our PEth testing in dried blood spots measures the 16:0/18:1 PEth species.
Why was one matrix positive and another negative on the same donor?
There are several explanations for this.
- Different sample matrices have different detection time frames. The result of any second collected specimen has no bearing on the validity of a first collected specimen. For example, a hair sample with a three month window of detection might test positive for a particular substance, while a urine sample from the same donor, with a 2-3 day window of detection, might test negative. In this case, the donor has used that substance within the past three months, but may not have used it within the most recent three days.
- The result of any second collected specimen has no bearing on the validity of a first collected specimen. Therefore, a negative result observed for the umbilical cord does not refute a positive result observed on the maternal urine specimen and the reverse is true as well. There are many legitimate reasons for discrepant urine and umbilical cord results.
- The urine specimen was a screen only result and was not confirmed using an appropriate mass spectrometric method. The screen only urine result is a clinically valid result, however, without an appropriate mass spectrometric confirmation, the urine result has no value in a forensic proceeding.
- Lastly, some placentas can prevent some compounds from reaching the fetus. There are documented cases of maternal ingestion without in utero exposure.
Annotated Bibliography for PEth 16-Apr-2014