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Medical Staff

D. Walt Chandler, PhD

Vice President, Labcorp; Executive Director, Endocrine Sciences

Dr Chandler received his PhD in biochemistry from the University of California, Los Angeles. He has more than 40 years of experience in diagnostic testing of steroid hormones and has been published in numerous professional journals. Dr Chandler is a past recipient of the National Institutes of Health Cell and Molecular Biology National Research Service Award. He is licensed by the state of California as a clinical chemist and certified as a New York State laboratory director. He is a member of the Endocrine Society, the Pediatric Endocrine Society, and the American Association of Clinical Chemistry.

Kelly Y. Chun, PhD

Vice President, Labcorp; Scientific Director, Endocrine Sciences

Dr Chun received her PhD in biochemistry from the Medical College of Wisconsin and trained as a postdoctoral fellow in laboratory medicine at Harvard Medical School. She has more than 20 years of experience in protein science and assay development and validation. She joined Esoterix in 2002 as a technical director. She oversees chemistry tests, endocrine immunoassays, and immunogenicity testing.

Over the years, Dr Chun has developed and validated a number of pivotal endocrine and autoimmune assays for pharmaceutical trial and clinical diagnostic use. She lectures on a national level and has authored articles and book chapters with a focus on endocrinology and immunogenicity. She is a member of the Endocrine Society, American Diabetes Association, and the American Association of Clinical Chemistry.

Brett Holmquist, PhD

Associate Scientific Director, Endocrine Sciences

Dr Holmquist is board certified by the American Board of Clinical Chemistry, a fellow of the National Academy of Clinical Biochemistry, licensed by the state of California as a clinical chemist, and certified as a New York State laboratory director. He earned his PhD in biochemistry and molecular biology from the University of California, Riverside.  He has worked for more than 25 years in the life science industry, including more than 12 years in the diagnostic laboratory industry. He is a member of the Endocrine Society, the American Society for Mass Spectrometry, the American Society for Clinical Pathology, the American Society for Clinical Laboratory Science, and the American Association of Clinical Chemistry.

Samuel H. Pepkowitz, MD

Medical Director, Endocrine Sciences

Dr Pepkowitz is board certified in pediatrics, anatomic pathology, and clinical pathology and has a special qualification in blood banking. He received his medical degree from the Columbia University College of Physicians and Surgeons. Dr Pepkowitz is a member of the American Academy of Pediatrics, the American Society of Clinical Pathologists, the College of American Pathologists, the American Medical Association, the American Association of Blood Banks, Pediatric Endocrine Society and the Society for Pediatric Pathology.

Steve B. Phagoo, PhD

Associate Scientific Director, Endocrine Sciences

Dr Phagoo received his PhD from Imperial College, University of London, in the United Kingdom. Overall, he has more than 25 years of experience in industry and research, with more than 15 of those years in clinical laboratory diagnostics, the in vitro diagnostics (IVD) industry, and method development. 

With a pharmaceutical industry and biochemistry background, Dr Phagoo has authored many publications, including the biochemistry and molecular signaling in inflammation, and was the recipient of numerous national- level awards and grants as an assistant professor at the University of Southern California. Dr Phagoo is a member of the American Diabetes Association, and the American Association of Clinical Chemistry (AACC) and is active on the board for the Southern California AACC section.  

Toni R. Prezant, PhD

Director of Molecular Genetics, Endocrine Sciences

Dr Prezant is board certified in clinical molecular genetics by the American Board of Medical Genetics and Genomics and is licensed in California and certified in New York State as a laboratory director. She earned her PhD in biology from the Massachusetts Institute of Technology. Dr Prezant has more than 12 years of clinical experience in molecular genetic testing and an extensive research background, including studies of mitochondrial DNA diseases and pituitary tumorigenesis. Dr Prezant develops and validates new tests for Endocrine Sciences’ molecular genetics laboratory. She is a member of the American Society of Human Genetics and the Association for Molecular Pathology.