Frequently Asked Questions

*Click the green and white plus sign beside each question to view the answer.

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 3.6.2.2.3.5 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.”

See the abstract for “Dried blood spot methods in therapeutic drug monitoring: methods, assays, and pitfalls” here

See FedEx guidelines for shipping clinical samples here

Please follow our collection instructions for DBS/Whole blood.

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 hair test be manipulated by the donor?

Yes. Bleaching, perming, dyeing and straightening can affect the outcome of a hair test. Cosmetically treated hair should not be collected.

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 hair test determine how much or how often someone is using a drug?

No. Hair is a reservoir matrix, where drugs can collect and/or degrade over time. When testing any reservoir matrix, you are unable to back-track and determine time, dosage or frequency because there are simply too many variables involved.

Can a nail test be used to prove that a previously taken hair test was inaccurate?

No, the result of any second collected specimen has absolutely no bearing on the validity of the result of any first collected specimen because you have no idea what the donor did between time A and time B.

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 drugs administered to the mother during labor or delivery be detected in the newborn’s meconium or umbilical cord tissue specimen?

Yes. Drugs such as fentanyl or morphine only take a few minutes to reach the meconium and umbilical cord tissue. Although we do not see it every time, we routinely pick up morphine administered to the mother during labor and delivery. The appropriate question is whether there is a prescription or medical record that can provide a reasonable explanation for the specimen to test positive.

Can I use the reported value (the number) from a hair, nail, meconium, umbilical cord tissue, or urine test to determine how much or how often someone is using a drug (either prescription of illicit)?

No. These specimen types act as reservoir, where drugs and their metabolites may accumulate and/or degrade over time. When testing any reservoir matrix, it is impractical to back-track to determine time, dosage, or frequency. There are too many variables involved. The reported values (the numbers) have no therapeutic or clinical value. You cannot use the number to estimate how much the donor used or to what extent the donor was exposed.

Can someone test positive in fingernail because of passive or environmental exposure?

Yes, environmental exposure versus ingestion must be resolved when interpreting drug tests using fingernails.

Can someone test positive in hair because of passive or environmental exposure?

Yes, drugs are incorporated into hair by three major routes: environmental exposure, sweat and sebum from the scalp and blood flow through the follicle. Environmental exposure however will only generate a positive for the parent drug. Example: methamphetamine only. The other two mechanisms lay down drug and drug metabolites. Example: amphetamine/methamphetamine positive.

Can the drug test 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?

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.

Can 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.

Can the use of any isopropanol (rubbing alcohol) containing product explain a positive ethyl glucoronide (EtG) or fatty acid ethyl esters (FAEE) result?

No. The use of any product that contains isopropanol, such as isopropyl rubbing alcohol will not explain the present of a direct ethyl alcohol biomarker such as EtG or FAEE. Isopropanol forms its own glucoronide, isopropyl glucoronide and does not interfere with the detection of EtG or FAEE.

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 race make a difference in hair testing results?

Hair color, not race, is one of the most important variables in determining the quantity of drug found in the hair. Dark hair binds drug tighter than light hair.

What is the detection window for drugs of abuse in meconium and umbilical cord and why?

The detection windows for meconium and umbilical cord have been established over time through experience as opposed to experimentation. Dose-response experiments using harmful addictive drugs with pregnant women would be highly unethical.

The detection window for most drugs of abuse in meconium and umbilical cord testing is up to approximately 20 weeks (some drugs such as methamphetamine may be less). Meconium begins to accumulate in the fetal gut near mid-term of the pregnancy; therefore prior to this time frame there is no meconium for the drug to become trapped in. The umbilical cord cutoffs were selected to emulate the positivity rate of meconium through side-by-side studies inferring a similar detection window.

Does the sample need to be frozen?

No, the sample may be shipped ambient.

Can the use of any isopropanol (rubbing alcohol) containing product explain an ethyl glucuronide (EtG) result?

No, the use of any product that contains isopropanol will NOT explain the presence of EtG. Isopropanol forms its own glucuronide, isopropyl glucuronide and does not interfere with the LC-MS/MS detection of ethyl glucuronide (EtG).

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

No, lidocaine will not explain a GCMS or LC-MS/MS confirmed positive cocaine or cocaine metabolite in any specimen type. The compounds are structurally very different and breakdown into different metabolites.

Can I use the reported value (the number) from a hair, nail, meconium, umbilical cord, or urine test to determine how much or how often someone is using a drug (either prescription or illicit)?

No. These specimen types act as a reservoir, where drugs and their metabolites may accumulate and/or degrade over time. When testing any reservoir matrix, it is impractical to back-track to determine time, dosage or frequency. There are too many variables involved. The reported values (the numbers) have no therapeutic or clinical value. You cannot use the number to estimate how much the donor used or to what extent the donor was exposed.

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?

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.

Can morphine administered to the mother during labor or delivery be detected in the newborn’s meconium or umbilical cord specimen?

Yes, drugs such as morphine only take a few minutes to reach the meconium and umbilical cord. Although we do not see it every time, we routinely pick up morphine administered to the mother during labor and delivery.

Have USDTL’s newborn test results been used in court cases?

Yes. Testing results are forensically defensible when they are “confirmed results” or results that went through confirmation testing. Forensic testing is performed through two separate, validated laboratory procedures based on different scientific principles. The first procedure screens the specimen using one scientific method, and the second procedure confirms the results using a different scientific method. As an accredited forensic laboratory, we confirm all positive screening test results and our procedures follow strict guidelines laid out and overseen by our accrediting bodies. Our test results have been upheld in court because we follow strict internationally accepted forensic protocols.

If a mother was prescribed a particular drug during her pregnancy will it produce a positive result in the newborn’s meconium or umbilical cord test?

Maybe. There is no guarantee that the drug is in the meconium or umbilical cord tissue at or above the threshold to positivity cutoff level. There are numerous factors that may affect the outcome such as dose, metabolism, medication taking compliance, and recall bias. The appropriate question to ask is IF the specimen is positive is there a prescription or medical record that provides a reasonable explanation. Just because a specimen is negative, does not prove that the donor was abstinent.

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 are newborn drug testing results reported to the hospital?

Results are reported through USDTL’s client access web portal or, for an additional cost, can be distributed via an approved Health Level Seven International (HL7) method. Under no circumstances are results given via telephone.

Is there a test that can differentiate between fetal exposure to heroin and fetal exposure to morphine during the birthing process?

Yes. The umbilical cord tissue or meconium from a baby whose mother was administered morphine during delivery will only be positive for morphine. The umbilical cord of a baby that is positive for Meconin and/or Monoacetylemorphine (6-MAM) in addition to morphine is indicative of heroin exposure.

What is Meconin and why is it important in newborn toxicology?

Morphine is the predominant metabolite of heroin, but morphine is also a stand-alone drug and a metabolite of codeine. Some mothers are provided morphine during delivery. Historically, there have been instances where heroin-using moms could not be distinguished from moms given morphine during delivery. Meconin is a contaminating constituent from the poppy that is present in heroin. Therefore, like Monoacetylmorphine – a metabolite of heroin, the presence of Meconin indicates the use of heroin and when found in newborn specimens, indicates fetal exposure to heroin.

How do drugs get into nails?

Drugs are distributed via the blood supply to the nail cells and the nail bed. Nails grow not only in length but in thickness as well. As the nail grows in thickness, it creates layers of drug history.

How long do I have to dispute a result?

USDTL saves negative specimens for seven days after initial accessioning. Seven days is longer than the customary three days that most labs retain negatives. This duration should allow clients a reasonable time to decide if dispute resolution is needed, to contact customer service and initiate the process. Positive specimens are stored frozen for one year following accessioning. Our Client Services Representatives will provide you with the necessary paperwork for you to sign and return to initiate the re-test process. Once the paperwork is in order, Client Services will return a re-test result to you in one to two working days. If you have any questions after receiving the results, please contact Client Services and they will either assist you or direct you to one of our forensic toxicologists to discuss the case with you.

What can our organization do if we strongly suspect that an individual was drug-exposed, but the specimen results came back negative?

All of USDTL’s clients can “dispute” a negative result and request a “re-test” for one or more specific drug classes that are suspected of being present. The re-test is a concept routinely used in workplace urine testing, where a subject disputes a positive result and requests a re-test, which is a re-confirmation of the specimen with a cutoff at 40 percent of the original confirmation cutoff. For non-workplace cases, clinical professionals may believe that drug exposure occurred and dispute the negative finding, which results in a re-confirmation of the disputed drug class at 40 percent of the confirmation cutoff. This re-test then becomes the result of record for the case.

To order a re-test, fax or email USDTL Client Services a re-test request on your letterhead and state the test(s) requested, the subject’s demographic information, the USDTL lab number and your contact information. You can also call Client Services with the case information. Our representative will provide you with the necessary paperwork for you to sign and return to initiate the re-test process. Once the paperwork is in order, Client Services will return a re-test result to you in one to two working days. If you have any questions after receiving the results, please contact Client Services and they will either assist you or direct you to one of our forensic toxicologists to discuss the case with you.

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 does using a forensic drug test help the child later in life?

There are several reasons why testing a newborn for potential substances is important. Early detection provides many more options than detection at a later stage in the child’s life including:

Early detection of alcohol biomarkers allows newborns to be identified and enrolled into early intervention and community programs. New programs are showing dramatic improvements in children identified earlier in life.
Detection of an exposed child can allow help, intervention and treatment to be offered to the mother, so that exposure during future pregnancies may be prevented.
The forensic identification of fetal alcohol exposure allows future corroboration of alcohol related disorders in childhood.

How long can drugs be detected in body hair?

Body hair has a different growth cycle compared to head hair. Body hair may go dormant and remain in place up to one year. A positive result reflects exposure up to 12 months.

How long can drugs be detected in head hair?

Once a drug is incorporated into hair, it begins to slowly leach out due to normal daily hygiene and exposure to the elements. Most drugs have disappeared by three months. Furthermore, the laboratory only analyzes the first 1.5 inches (3.9 centimeters) nearest the scalp. Hair grows at an average rate of 0.5 inches per month.

How long does the laboratory keep remaining specimens?

Generally, negative specimens are kept for 7 days, and confirmed positive specimens are kept for 1 year.

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.

How much breast milk is needed?

Requested sample volume is 10 milliliters collected in a sterile container.

How much fingernail needs to be collected?

The optimum amount of nail clippings needed is 100 milligrams. If trimming all 10 fingernails, each clipping must be at least 2 millimeters to 3 millimeters long.

How much is needed for an adequate urine sample?

Requested sample volume is 10 milliliters.

How much meconium is needed for the test?

A minimum of 3 grams of meconium (about a teaspoon) is normally required. However, for best results, we recommend collection of the entire passage of meconium until the milk stool appears.

If a mother was prescribed a particular drug during her pregnancy will it produce a positive result in the newborn’s meconium or umbilical cord tissue test?

Maybe. There is no guarantee that the drug is in the meconium or umbilical cord tissue at or above the threshold to positivity cutoff level. There are numerous factors that may affect the outcome, such as dose, metabolism, medication compliance, and recall bias. The appropriate question is whether there is a prescription or medical record that can provide a reasonable explanation for the specimen to test positive. A negative specimen does not prove that the donor was abstinent.

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 time frame in which meconium must be collected for testing?

Only with regard to being able to test for fatty acid ethyl esters (FAEE), the ethyl alcohol biomarker in meconium. To be able to test for FAEE, the meconium specimens must be collected within 18 hours after birth. All other drug testing can be done on meconium regardless of when the meconium is passed as long as it is meconium that is being collected and not milk stool.

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.

Why are both ethyl sulfate (EtS) and ethyl glucuronide (EtG) included in urine testing for alcohol use, but only EtG in fingernail or hair testing?

A: For urine testing, it is standard practice in the field of toxicology to include both EtS and EtG, because EtG is subject to bacterial production and degradation if a urine sample is contaminated (e.g. when the donor has a urinary tract infection). EtS is not subject to bacterial production or degradation, and provides a second, more reliable alcohol biomarker in these urine contamination scenarios. Other specimens types, such as fingernails and hair, do not have this issue, so only EtG is measured in those sample types.

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 are the meconium specimen storage requirements?

Drugs and metabolites are stable in meconium for up to 2 weeks at room temperature. Storage in a refrigerator or freezer is preferred. Alcohol biomarkers specifically fatty acid ethyl esters (FAEE), are sensitive to heat and light; therefore, the preferred shipping method is frozen on dry ice. Since shipping via this method is both difficult and expensive, most institutions send specimens at room temperature and realize that the FAEE concentrations may be reduced. USDTL accept specimens that are shipped at room temperature.

What does a positive hair test result mean?

The only interpretation that can come from a positive hair test is that the individual used or was exposed to drug during the three months prior to collection.

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 Child Hair Testing, and how is it different from regular hair drug tests?

Child Hair and Nail Testing are a modified hair and nail drug tests designed to increase environmental exposure detection in children. The assays are often used by social service agencies involved in custody cases.

What is meta-hydroxybenzoylecgonine (m-OH-BZE)?

Meta-hydroxybenzoylecgonine (m-OH-BZE) is a metabolite of cocaine which is often present in the meconium of neonates born to cocaine-using mothers. It is a minor metabolite in adults, but it has been identified as the only cocaine metabolite present in 23 percent of meconium specimen screening positively for cocaine.*

*Reference: Lewis D, Moore C, Becker J, Leikin J. Prevalence of meta-hydroxybenzoylecgonine (m-OH-BZE) in meconium samples. Bulletin of the lnt.Ass.Forens Toxicol 1995;25(3):33-36

What is the detection window for urine?

A sample of urine provides a drug history from the last two to three days for most drugs, and an even longer period for marijuana.

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 turnaround time for testing results?

Generally, the standard turnaround time for reporting negative screening test results is the next business day, with an additional 1-2 business days for specimens that require confirmatory testing. Turnaround time begins from receipt of the valid specimen -accompanied by a properly documented valid order- into the laboratory. Some tests require additional time to process and will fall outside the standard turnaround time window.

What is the window of detection for PEth?

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

What is the window of drug exposure for drugs of abuse in meconium and umbilical cord tissue and why?

The detection window for most drugs of abuse in meconium and umbilical cord tissue testing is up to approximately 20 weeks prior to birth. Meconium begins to accumulate in the fetal gut near mid-term of the pregnancy. Prior to this time frame there is no meconium to trap the drug or drug metabolites. The umbilical cord tissue cutoffs were selected to emulate the positivity rate of meconium through side-by-side studies inferring a similar detection window.

What newborn alcohol tests are available at USDTL?

USDTL offers three different tests that can be used for detecting direct ethyl alcohol biomarkers in newborns.

Ethyl glucoronide (EtG) can be detected in umbilical cord tissue with a window of detection up to approximately 20 weeks prior to birth. EtG can be tested in umbilical cord tissue as a stand-alone test or it can be added to any umbilical cord tissue panel.
Fatty acid ethyl esters (FAEE) can be detected in meconium with a window of detection up to approximately 20 weeks prior to brith. FAEE can be tested in meconium with a window of detection up to approximately 20 weeks prior to birth. FAEE can be tested in meconium as a stand-alone test or it can be added to any meconium panel. Collection must occur within the first 18 hours after birth to be viable for FAEE testing. See the meconium collection instructions for details.
Phosphatidylethanol (PEth) can be detected in blood. Collection is done via heel stick on a dried blood spot card anytime during routine newborn screenings. It has a unique window of detection in blood up to approximately 2-4 weeks prior to collection.

What type of alcohol wipes should I use?

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

When will I receive breast milk results?

Results will be provided in two to three days after the sample is received in the laboratory.

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 do we test for EtG in hair and not FAEE?

FAEE is less sensitive and can produce false positives. Hairspray and other hair products can produce FAEEs in hair. There is no enzyme in our hair that can create ETG from those products.

Will a UTI affect the result of drug and/or alcohol testing?

Certain bacteria may interfere with drug detection but will not generate a false positive. Fermenting bacteria in the presence of excess glucose may produce ethanol in the bladder and in the specimen cup.

Will drugs administered or taken by the mother affect the newborn drug test result?

Any drugs administer or taken during pregnancy, labor, or delivery have a possibility of being detected. The appropriate questions is whether there is a prescription or medical record that can provide a reasonable explanation for the specimen to test positive.

Will one-time drug use be detected in Fingernail Testing? How many times would they have to use drugs for it to be detected in nails?

Single doses do not guarantee a positive result. The number of doses required to generate a positive result is highly variable between donors.

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.

Contact USDTL

1.800.235.2367