Why is Confirmation Testing Necessary?

Confirmation testing using a second portion of specimen serves two main purposes.

by Joseph Jones, Ph.D., NRCC-TC

When a newborn is selected for meconium or umbilical cord drug testing, a number of events are set into action. In most hospital settings, the selection follows at least one observation that has led to a suspicion of prenatal drug exposure. These observations include history of maternal drug use, prostitution, sexually-transmitted diseases, lack of prenatal care, unexplained placental abruption, unexplained premature labor, admission to the neonatal intensive care unit, and the observation of withdrawal symptoms. It has been reported that these observations could be an indication of prenatal drug exposure.  

The suspicion of prenatal drug exposure raises the bar for newborn drug testing because a positive result is expected. A positive result, in most jurisdictions, requires mandatory reporting of this information to the State, moving a newborn drug test out of the realm of clinical testing and into the realm of forensic testing. Therefore, at the time the drug test is ordered, the ordering party assumes the responsibility of a State Actor, a person acting on behalf of a government body. With this foreknowledge, the test should be analyzed according to commonly accepted guidelines for forensic drug testing, which includes (1) documenting a chain of custody and (2) performing confirmation testing using a second portion/aliquot of specimen and a different analytical method (if available). The importance of chain of custody was detailed in a previous article, and is available on our website, titled Who Cares About Chain of Custody?

Confirmation testing using a second portion of specimen serves two purposes. First, a confirmation test mitigates frame shift errors. If a specimen were switched during an initial testing run, this discovery would not be detected. However, for a specimen that did not screen negative, repeating the process with a second portion/aliquot of specimen would reveal the frame shift error if the two results do not agree. Confirmation results that do not agree with the initial test results alert the laboratory to the possibility of a frame shift error so an investigation of the event can be initiated.

The second purpose of confirmation testing is the use of a second (typically more specific) analytical methodology when available. The initial test is generally a sensitive, and quicker test used for the purpose of weeding out the negatives. The more time consuming and specific techniques (such as GCMS and LCMSMS) are reserved for confirmation of the specimens that did not screen negative. This strategy of “screen and confirm” is standard in the forensic drug testing industry.  

Our umbilical cord test is a great example of “screen and confirm” using different analytical techniques. We use an immunoassay technique, which is very sensitive and relatively fast, for the initial screen test. All specimens that do not screen negative are then confirmed by gas chromatography/mass spectrometry, gas chromatography/tandem mass spectrometry (GCMS, GCMSMS), or liquid chromatography/tandem mass spectrometry (LCMS), which are slow, but are the gold standard techniques for confirming drugs of abuse in a variety of biological fluids and tissues.  

An example of a “screen and a confirm” using the same analytical technique is the detection of Fatty Acid Ethyl Esters (FAEE) in meconium.  An immunoassay does not exist for FAEE detection; therefore, all specimens are screened using the more specific GCMS techniques. All specimens that do not screen negative are then confirmed with a second portion/aliquot of specimen using GCMS as well.

Forensic drug testing laboratories work with the oversight of forensic accrediting bodies. These accrediting bodies review the laboratory processes regularly for accuracy and compliance. Laboratories that don’t have proper oversight can put an organization’s reputation and integrity at risk if their processes are determined to be forensically indefensible (i.e. the results don’t hold up in court). This can lead to extensive and costly reevaluation. USDTL holds one of the highest international accreditations for forensic toxicology as an ANSI-ASQ National Accreditation Board (ANAB) ISO 17025 forensic testing laboratory. This means that every test completed by USDTL is done so under the highest standards available for a forensic drug testing laboratory.

References

1. Moffat, A. Osselton, M., Widdop, B., Jickells, S., & Negrusz. (2013). Introduction to Forensic Toxicology.  Cooper, G., & Negrusz, A. (Eds.). (2013). Clarke’s analytical forensic toxicology. Pharmaceutical Press.

2. Guidelines for the Forensic analysis of drugs facilitating sexual assault and other criminal acts. (2011). Retrieved 2017, from United Nations Office on Drugs and Crime, https://www.unodc.org/documents/scientific/forensic_analys_of_drugs_facilitating_sexual_assault_and_other_criminal_acts.pdf

3. Society of Forensic Toxicologists and American Academy of Forensic Sciences (2006). Forensic Toxicology Laboratory Guidelines, 2006 Version.  Retrieved from: http://www.soft-tox.org/files/Guidelines_2006_Final.pdf

4. Cary, P. (2011). The fundamentals of drug testing. The Drug Court Judicial Benchbook, D. Marlowe & W. Meyer, Eds., 113-138. Retrieved from: http://www.ndci.org/sites/default/files/nadcp/14146_NDCI_Benchbook_v6.pdf

5. National Forensic Science Technology Center. (2016). A Simplified Guide to Forensic Toxicology. Retrieved from: http://www.forensicsciencesimplified.org/tox/Toxicology.pdf

6. College of American Pathologists. (2013). Forensic Drug Testing Checklist. College of American Pathologists: Northfield, IL.

Dr. Joseph Jones is the Chief Operating Officer and Executive Vice President for USDTL with more than 25 years of experience in the forensic toxicology industry. Jones has provided expert testimony in a variety of venues throughout the country and appears as an author on over a dozen peer-reviewed scientific articles. Jones is listed by The National Registry of Certified Chemists as a Toxicological Chemist, CAP Laboratory Inspector, and qualified as an expert in drug testing in several venues including union arbitration, unemployment hearings, family court, civil court, criminal court and Military courts-martial and frequently gives workshops, presentations and webinars.