An outspoken advocate for clinical mass spectrometry
In recent years, Vitamin D testing has become one of the most common clinical laboratory tests performed – and for good reason. Vitamin D plays a role in, not only calcium and bone metabolism, but potentially in diabetes, cardiovascular disease, multiple sclerosis, cancer, psychiatric disorders, and neuromuscular disease.
But there’s a problem with FDA-approved immunoassay testing, the predominant means of measuring Vitamin D concentration in blood, according to Dr. Robert Fitzgerald.
“Any reasonably objective person that examines immunoassay data testing for vitamin D concludes that the error in some of those tests is plus or minus 40 percent,” said Fitzgerald. “If you're really concerned about a vitamin D concentration, in my view, it really leaves doing it by mass spectrometry.”
Dr. Fitzgerald is a forceful advocate for the use of mass spectrometry in clinical testing at his toxicology laboratory at the University of California San Diego Medical Center.
“The primary role of our laboratory is patient care,” he explained. “Immunoassay drug screens can tell you if a class of drugs is present, but they don’t identify the specific drug(s) . In certain situations it’s important to know the exact identity of the drugs in a patient’s specimen. So, we identify and quantify drugs that are present using liquid chromatography with tandem mass spectrometry. We also do small molecule quantitation work, with vitamin D testing as our largest workload. Another major component of our efforts is new method development.”
Immunoassays: fast, affordable – and unreliable
Dr. Fitzgerald’s advocacy for more accurate mass spectrometry testing first gained attention in 2003, when he and his colleague David Herold wrote an editorial in Clinical Chemistry entitled “Immunoassays for Testosterone in Women: Better than a Guess?” The editorial pointed out that automated testosterone immunoassays were shown to be inaccurate by 200% to 500% – and thus of little value.
Ever since then, Dr. Fitzgerald has been driven to improve the quality of clinical testing.
“I want to make sure the results we produce are reliable, accurate, and reproducible,” said Dr. Fitzgerald. “Sometimes clinicians make life-changing decisions based on our tests. So all of them have to be right.”
Dr. Fitzgerald is part of a team responsible for three laboratories: two rapid-response labs in the UCSD hospitals, and a third reference lab at the UCSD Center for Advanced Laboratory Medicine. All told, the facilities perform about 4.5 million reportable tests per year, with the toxicology lab handling about 40,000 tests annually.
With that volume, Dr. Fitzgerald has been encouraged by the productivity gains made in mass spectrometry in recent years.
“The biggest change, at least affecting my lab, has been the development of atmospheric pressure ionization, electrospray in particular,” he noted. “That dramatically simplified sample preparation. Sample preparation used to be the rate-limiting - and most expensive - step, now, the rate-limiting step really is chromatographic run time. And with the development of ultra-performance liquid chromatography, you get a much shorter run time, and again, increased efficiency and throughput. The sensitivity improvements have also been astounding.”
Training the next generation of leaders
Dr. Fitzgerald is equally committed to sharing his mass spectrometry expertise with colleagues.
“My second priority is training,” he explained. “We are an academic institution and as such we train resident physicians, PhD-level lab directors and clinical laboratory scientists. A combination of outstanding faculty along with the right mix of patient specimens, provides an fantastic opportunity to learn laboratory medicine.
The UCSD ComACC accredited clinical chemistry training program is supported by Waters. In 2013 Waters announced its sponsorship of the two-year postdoctoral Clinical Chemistry Fellowship at the University of California San Diego School of Medicine. While in the program, fellows collaborate with the California Poison Control Center and the UC San Diego Medical Toxicology program to gain experience in toxicology in addition to training in clinical chemistry which prepares them for certification by the American Board of Clinical Chemistry. The program has graduated two fellows to date.
“They learn an immense amount about laboratory medicine and they develop an identity as part of a healthcare team,” said Dr. Fitzgerald. “That’s why the Waters’ funding is so important, because there are no federal funds to support development of clinical chemists. And if you look at healthcare and optimal use of resources, laboratorians play a big role in examining over-testing as well as under-testing -- making sure the right tests are ordered for the right patients. Having the ability to train the next generation of leaders is one of the things that brings me to work every day. It’s exciting to work with smart people who are developing a passion for patient care through the use of analytical chemistry.”
An inexorable path to the laboratory
The son of a physician and a nurse, Rob Fitzgerald grew up with five siblings on the rural Eastern Shore of Maryland. Although surrounded by medical science as a child, he didn’t take an avid interest in it until 12th grade.
“It started out with a high school chemistry teacher, Ron Peterman,” he recalled. “I took AP Chemistry and he piqued my interest. My older sister had said how cool he was, how wonderful it was, how much she learned.”
That led to an interest in forensic chemistry at Loyola College of Maryland, where he had “another advisor, Henry Friemuth, who was a toxicologist and one-on-one sessions with him convinced me to do forensic toxicology.” After earning his BS in Chemistry, he pursued his doctorate in Pharmacology/Toxicology at the Medical College of Virginia/Virginia Commonwealth University under the guidance of Alphonse Poklis and Robert Blanke.
Dr. Fitzgerald made the move to California in 1992 and spent 19 years at the UCSD affiliated San Diego VA Hospital as Director of the Mass Spectrometry
Laboratory before switching to the UC San Diego Center for Advanced Laboratory Medicine
When he’s not in the laboratory, Dr. Fitzgerald gravitates toward the ocean.
“I’m fortunate to live here in Southern California where we get really good waves,” he noted. “So I get a chance to surf frequently and when the surf is flat, I like spending time on the water kayak fishing, or fishing in general.”
New clinical uses for mass spectrometry
Looking ahead, Dr. Fitzgerald sees lots of opportunities to expand the use of mass spectrometry in the clinical setting. In addition to how MALDI has changed the microbiology laboratory, electrospray mass spectrometry offers the potential to improve the sensitivity and specificity of many assays. Mass spectrometry is rapidly moving from a specialized service into routine clinical practice.
“One of the current opportunities for mass spectrometry is protein quantitation,” noted Dr. Fitzgerald. “Our whole grand rounds this morning was focused on the inability of immunoassays to correctly identify recurrence of thyroid cancer. If you have thyroid cancer, they often remove your thyroid gland and they look for a molecule called thyroglobulin after surgery. If you remove the thyroid gland, the patient’s thyroglobulin should become undetectable because the gland is the only source of thyroglobulin. In this case, thyroglobulin is being used as a cancer marker; if your thyroglobulin becomes elevated following surgery, then this indicates that cancer has probably returned. Unfortunately many of these patients develop antibodies against thyroglobulin, which confuses the immunoassay. The patient’s antibody covers up the epitope that the immunoassay binds to, causing a false negative result. In this case the cancer has returned, but the physician does not know it.
“One of the solutions to this is to digest the patient’s sample and use mass spectrometry to look for peptides that are indicative of thyroglobulin. At present, mass spectrometry has not provided all of the answers in this setting, but the technique holds a lot of promise. I think that protein quantitation is where clinical mass spectrometry could make a huge impact in the future.”
In this Letter to the Editor in the journal Clinical Chemistry, Dr. Fitzgerald asks "How can assays that are grossly inaccurate gain approval for use in diagnosis and treatment of endocrine abnormalities?" and argues for the adoption of more accurate testosterone assays.
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