Ask the Tox

Some of our most frequently asked questions answered by one of USDTL’s leading toxicologists, Joseph Jones, Ph.D., NRCC-TC. 

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.

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).

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?

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 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.

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 umbilical cord drug test results been used in legal proceedings?

Yes, the first case that used the detection of drug metabolite as evidence of maternal use of cocaine was in a 2003 South Carolina case.¹ This interpretation was upheld on appeal to the South Carolina Supreme Court.²

Since the launch of umbilical cord tissue testing in October of 2007, USDTL has conducted over 105,000 umbilical cord analyses from almost every state in the union and many of those analyses have been used in legal proceedings where we were not made aware of its use or outcome. However, there have been 9 instances where the results were challenged and USDTL was asked to provide testimony. At the time of the writing of this document, umbilical cord tissue drug testing results have been challenged and successfully used in Colorado, Nebraska, Utah, Iowa, and Illinois.

Is the umbilical cord newborn tissue or maternal tissue?

Umbilical cord is genetic material of the newborn. The umbilical cord is formed from fetal origins during the first 5 weeks of gestation.^3,4,5

References

1. State v. McKnight, 352 S.C. 635, 576 S.E.2d 168 (2003).

2. McKnight v. State, No. 26484 (SC, 2008)

3. C. Blakemore, S. Jennett (Eds.), The Oxford Companion to the Body, 1st edition, Oxford University Press, New York, 2001, p. 700.

4. B. Pansky, Dynamic Anatomy and Physiology, Macmillan Publishing Company, New York, 1975, p. 619.

5. P. Williams, R. Warwick, M. Dyson, L. Bannister (Eds.), Gray’s Anatomy, 37th edition, Churchill Livingstone, New York, 1989, p. 143.