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Adult & Child Drug Testing Lab

Adult PEth Testing

Animation of Ethanol exposed to red blood cell membranes

Dried Blood Spots

Dried Blood Spot (DBS) collection is the fastest, most convenient way to test for phosphatidylethanol (PEth) Glossary Icon 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 up to approximately 2-4 week history of alcohol (ab)use. We offer PEth testing in both dried blood spots and whole blood. The specimen 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 non-ethanol-based alcohol 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 barcode 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 the 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 phosphatidyl ethanol species 16:0/18:1) is an indication of alcohol exposure up to approximately 2-4 weeks prior to specimen collection.



Whole Blood Alcohol Biomarker Testing is available upon request.



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By Phone: 1.800.235.2367

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Monday 7am-7pm
Tuesday 7am-7pm
Wednesday 7am-7pm
Thursday 7am-7pm
Friday 7am-7pm
Saturday 8am-5pm

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Are there any special restrictions on mailing PEth tests from HIV-positive blood?

There are no special instructions for shipping dried blood spots. The IATA Infectious Substances Shipping Guidelines (ISSG) address shipping dried blood spot as an exception under section which states:“Dried blood spots, collected by applying a drop of blood onto absorbent material, or faecal occult blood screening tests and blood or blood components which have been collected for the purposes of transfusion or for the preparation of blood products to be used for transfusion or transplantation and any tissues or organs intended for use in transplantation are not subject to these Regulations.”

Are the PEth collection supplies CLIA-waived?

The collection supplies that we have are not CLIA-waived, as we are a CLIA accredited laboratory and must follow all accreditation standards.

Are you aware of any other labs splitting specimens for PEth or sending two specimen cards filled with dried blood for testing?

There are no other labs that do commercial dried blood spot PEth testing, so there are no labs for comparison.

Can a second test of a different specimen type be used to prove that a previously taken test was inaccurate?

No. The results of any second collected specimen have absolutely no bearing on the validity of the results of the first collected specimen. Furthermore, each matrix has its own advantages, disadvantages and limits of interpretation.

Can a single serving of ethanol alcohol (12 oz. beer, 5 oz. wine), cause a positive Phosphatidylethanol (PEth) using a 20 ng/mL cut-off in whole blood or dried blood spot?

The literature suggests that it requires multiple servings of ethanol on a single occasion to produce a positive PEth result. PEth has a half-life of approximately 4.5 days.

Can the use of isopropanol (rubbing alcohol) containing product explain a positive PEth result?

There are zero instances in the scientific literature (over 25,000 articles) of anything other than consumption of ethanol creating Peth results.

Can we order just the blood spot cards?

Yes, during your account setup process just inform us that you will only need the blood spot cards.

Can we purchase the collection supplies for training purposes?

We do not sell collection supplies. All account set-up paperwork must be completed before we ship the supplies to your facility.

Can we transfer whole blood specimen to the blood spot card?

Whole blood can be submitted for PEth testing by sending in the whole blood tube. We do not recommend transferring blood collected under a chain of custody via venipuncture to a dried blood spot card.

Do you have any recommendations on how to ship specimens internationally?

We are not able to help with any of the shipping coordination or additional questions regarding international testing as we do not know the local laws.

Do you require a Chain of Custody Form for research specimens?

No. Chain of Custody Forms are not used for research specimens.

A manifest form is required in this case. Identification numbers and dates are required on the manifest. Click here to see a sample manifest form.

Please note that:

  • ID numbers on the manifest must match the ID on the specimens.
  • 2 unique numbers are preferred, if not possible, one unique number is acceptable.

Does the sample need to be frozen?

No, the sample may be shipped ambient.

Does the use of Xylocaine® (lidocaine) explain a positive cocaine or cocaine metabolite in any specimen type?

No, Lidocaine will NOT explain a GCMS or LCMSMS confirmed positive cocaine or cocaine metabolite in any specimen type (blood, urine, hair, nails, meconium, umbilical cord segment, etc…). The compounds are very structurally different and breakdown into very different metabolites.

Can the drug test result from a maternal specimen (such as maternal hair, nail or urine) differ from the result from a neonatal specimen such as neonatal urine, meconium or umbilical cord tissue segment?

Yes, the results can be different. Each specimen type has its own advantages, disadvantages, threshold to positivity, and detection time window. One test does not refute the other. The test results are cumulative. For instance, if the maternal urine is positive for cocaine and newborn meconium is positive for methamphetamine, the results do not rule each other out. The appropriate interpretation is that the mother consumed both cocaine and methamphetamine.

Have results been used in court cases?

Yes, the analysis of a number of tissue types for the presence of drugs of abuse has been used in every state for decades. Specifically, our umbilical cord testing has been used to provide evidence of drug use by the mother in numerous states. Additionally, the detection of drug in umbilical cord was used as evidence of maternal drug consumption in a murder case in South Carolina and that interpretation was upheld on appeal to the SC Supreme Court.

Have you ever had any challenges to positive PEth test results in whole blood and/or dried blood spot?

Extensive research has helped create a good understanding of PEth and how it can be utilized both in research and commercially. This has helped eliminate major challenges that other, less researched assays, might face.

How do PEth results differ from Urine EtG/EtS results?

Recent studies have indicated that low-level positive EtG results can be produced by certain agents like hand sanitizers and mouth wash (incidental exposure). Research indicates that the volume of alcohol required to trigger a positive PEth result is far above the level available from incidental exposure.

How does a PEth test result correlate with “dangerous” versus “social” drinking?

The testing can only detect whether PEth is present in the specimen, it cannot determine time, dose, or frequency of use. The literature suggests that it requires multiple servings of ethanol on a single occasion to produce a positive PEth result.

How much blood is required for a PEth testing specimen?

5 individual large drops on a dried blood spot collection card or 5 milliliters of whole blood collected in a gray-top collection tube containing anticoagulant.

If the quantity of drug or alcohol metabolite detected is high, could that be an indication that the donor (1) was consuming a large amount, (2) was using recently, or (3) was using frequently?

There are too many variables for anyone to know time of use, dosage, or frequency from the result(s) of a drug test. Reservoir matrices such as hair, fingernail, umbilical cord, and meconium continuously collect drug and alcohol biomarkers. This makes it difficult to determine specific details of use. Because the biomarker is collected over a period of time, the results represent total accumulation that cannot be pin-pointed to specific times/dates/dosages, etc.

Is testing PEth in dried blood spot and whole blood the same price?

Yes, the price is the same whether it is whole blood or dried blood spot.

Is there a proportion of consumption related to each increasing result? i.e. is 100 ng/mL 5 times more consumed than a 20 ng/mL result?

Testing can only detect whether PEth is present in the specimen, it cannot determine time, dose, or frequency of use. PEth has a half-life of 4.5 days so the results are contingent on when the donor last drank and how much they have been drinking.

Is there a specific shipping company we would need to use or is that at our discretion?

You may use any shipping courier of your choice.

Is there a timeframe in which collected PEth specimens can no longer be tested for research purposes?

With strictly research specimens, our laboratory has more flexibility regarding testing timeframes. In general, specimens should not be tested beyond their stated timeframe for stability. The Sponsor should note that any results from testing specimens beyond their stated timeframe for stability can be less reliable.

May the reported quantitation of drug or metabolite in hair, nail, meconium, umbilical cord, or urine be used to determine the timing of the drug use, how often the donor uses the drug, or the extent of the donor’s drug use?

No. When testing a reservoir specimen type, a specimen type where analytes tend to accumulate, you may not backtrack to determine time, dosage, or frequency. The result is positive or negative for the appropriate detection window associated with the specimen type.

Should I keep the collected dried blood spot specimens in a cooler or just at room temperature?

Please keep specimens at the normal air-conditioned lab temp ±26 degrees Celsius or in the fridge.

What does a positive PEth mean? Does it measure only heavy/binge drinking or will it be positive after consuming a drink per day over a few days?

A positive PEth result means that the donor has consumed ethanol sometime during the last 2-4 weeks (approximately).

What does USDTL provide in the PEth dried blood spot collection supplies?

  • 2 blood spot lancets
  • 2 tamper-evident seal
  • 2 non-ethanol based alcochol pads
  • 1 blood spot card
  • 1 blood spot drying box

What is the length of time PEth dried blood spot specimens can be stored while still maintaining their integrity?

  • Room Temp = 1 year
  • Refrigerated = 1 year
  • Frozen = 1 year at 20ºC (-4ºF)

What is the length of time that specimens can be stored while still maintaining their integrity?

Dried blood spot cards can be stored up to 1 year at room temperature, refrigerated, or frozen. Whole blood tubes can be stored for 1 week at room temperature, 1 week refrigerated, or up to 1 year frozen (can be thawed up to 3 times).

What is the longest time PEth will remain positive after problem drinking stops?

The Peth test is designed to detect heavy drinking up to approximately 2-4 weeks prior to collection. This is because PEth has an average half-life is 4.5 days. This means that every 4.5 days the level of Peth is cut in half. For example: If an average person with a PEth level of 1000 ng/mL stops drinking, it would take approximately 2.5 weeks for them to fall below the 20 ng/mL cut-off level.

What is the minimum shipment requirement for PEth specimens for research purposes?

Please send at least 10 or more specimens per batch; preferably overnight with tracking capability. You can use any courier of your choice. Please have specimens arrive at USDTL between Monday and Friday.

What is the window of detection for PEth?

Up to approximately 2-4 weeks depending on the starting concentration of PEth.

What type of alcohol wipes should I use?

ONLY use isopropyl alcohol wipes. DO NOT use any wipes or sanitizers that contain ethyl alcohol.

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.

  1. 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.
  2. 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.
  3. 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.
  4. Lastly, some placentas can prevent some compounds from reaching the fetus. There are documented cases of maternal ingestion without in utero exposure.

With 5 dried blood spots, are all 5 spots used for testing PEth?

We typically use 2-3 of the blood spots for testing (assuming all five circles are filled). Ideally, there will be 1-2 blood spots left over and stored in the event a retest is requested.

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Client Services

By Phone: 1.800.235.2367
Business Hours (CST)
Monday....................7am-7pm Tuesday....................7am-7pm Wednesday.............7am-7pm Thursday..................7am-7pm Friday........................7am-7pm Saturday...................8am-5pm

Contact Client Services

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