American Association for Clinical Chemistry
Better health through laboratory medicine
May 2009 Mentor of the Month Q&A Session: Marilyn Huestis
Welcome to SYCL's Mentor of the Month.  Questions and Answers will be displayed below...

Thank you Dr. Huestis for a wonderful interview. You mentioned that as “analytical techniques become more sensitive, the emphasis will be less on obtaining the lowest quantitative numbers and more on accurate interpretation of the meaning of the data.” In dealing with TDM and toxicology, it seems that physicians prefer to be given a “number.” Do you have any examples or suggestions on how one can begin to enter into a dialogue with physicians and break the practice of just reporting numbers? Thanks.
Nancy, New Mexico

Marilyn Huestis
I think the key is to develop a trusting working relationship. One of doing this is to offer to give educational inservices to the physician staff on important laboratory tests and their interpretation. The value of a number is going to be based on the type of testing involved- i.e. regulated workplace drug testing, drug treatment testing, clinical toxicology or even post-mortem testing. Being able to show your expertise and to be able to discuss knowledgeably potential interpretations will provide a valuable resource for your clinical staff. In addition, you might consider opportunities for abstracts or manuscripts that could be derived from your laboratory work and share authorship with the physicians. This might be a positive step for both your careers and also builds constructive bridges with the clinical staff. Another approach would be to discuss alternative matrices for different applications, including advantages and limitations of each. Getting away from just reporting numbers and providing expert interpretation of the results is a more rewarding position for the chemist and provide an important resource for the clinical team.

Hello Dr. Huestis, I found your interview very interesting. Could you please share with us your thoughts regarding opiate screening? As mass spectrometry begins to replace the less sensitive and specific immunoassay screens, should toxicology labs begin using lower cut-offs to identify positive patients when using mass spectrometry? Thank you.
Anthony, Canada

Marilyn Huestis
There is not a simple answer to your interesting question. First, LCMS and GCMS are certainly more specific than an immunoassay, but in general you need to consider workload, personnel staffing, type of testing- workplace, clinical toxicology, drug treatment monitoring, newborn screening etc, to give an answer. The turnaround time may also be a critical factor in emergency toxicology. Regulations may require a particular type of testing and/or a specific cutoff concentration- i.e. for workplace testing. For newborn screening of urine, amniotic fluid, meconium and/or hair- the highest sensitivity may be important for identifying in utero drug exposure. For emergency toxicology, the physicians may only be interested in drugs that could be contributing to an overdose situation. If you eliminate immunoassay screening, do you have enough highly trained staff available to operate the mass spec 24/7? Turnaround may be critically important. How will you interpret really low concentrations of opiates? There is nothing wrong with cost savings if adequate equipment and personnel are available to have mass spectrometry available around the clock. A great advantage of mass spec for opiates is the ability to quantify opiates that may not be detected in an immunoassay, such as oxycodone, buprenorphine and others that fail to cross-react in the opiate assay. This is especially true if multiple immunoassays are required to give a full screen. Another aspect to consider is the need to hydrolyze glucuronide and sulfate analogs prior to mass spec. Many opioids are highly glucuronidated and could be missed if hydrolysis is eliminated. Thus, there are many different aspects to your question that require a thoughtful approach to workload, staffing, turnaround times and purposes of testing. Thanks for asking.