Our Medical Review Officers

FirstLab's distinguished medical team leads the healthcare industry with ongoing thought leadership and innovation.

Thought leaders. Innovators.

The depth and breadth of our medical team's collective experience is unrivaled. They are keynote presenters at industry conferences, published authorities in their field, and pioneers who forge new ways of thinking.


Natalie P. Hartenbaum

M.D., M.P.H., F.A.C.O.E.M.
Chief Medical Review Officer

Dr. Hartenbaum is recognized as a national expert in occupational fitness for duty with a special focus on transportation. She has extensive experience in multiple occupational medicine settings, including corporate, clinical and academic. She has given over 100 professional presentations and lectures at medical meetings, conferences, transportation forums and other seminars. She has authored, edited, or contributed to numerous published articles, papers or books in the Occupational and Environmental Medicine field.

Dr. Hartenbaum was appointed Chief Medical Review Officer of FirstLab in December 2005. She has overall responsibility for the medical review and interpretation of workplace drug tests. She also coordinates the MRO services of FirstLab's staff of certified MROs and MRO assistants.

Dr. Hartenbaum is Board Certified in both Internal Medicine and Occupational Medicine. She received her B.A. in Biology from Temple University, her M.D. from Temple University School of Medicine, and a Master's of Public Health (M.P.H.) in Occupational Medicine from the Medical College of Wisconsin.


James Ferguson

D.O., FASAM
Medical Director and Addiction Specialist

Dr. Ferguson literally wrote the book on being an MRO. A certified MRO since 1992, he is the author of The MRO Team Manual and co-author of the MRO chapters of the Principles of Addiction Medicine and the Handbook of Workplace Drug Testing. He is also the course director for the American Society of Addiction Medicine Comprehensive MRO Training Courses. Prior to this, he spent 13 years practicing emergency, general and addiction medicine.

Dr. Ferguson is the Medical Director for FirstLab's Recovery Management Services (RMS) Division. He provides advice and counsel on all aspects of RMS drug and alcohol testing programs and coordinate FirstLab's RMS information and education initiatives. 

Dr. Ferguson received his undergraduate degree from the University of Washington and his Doctor of Osteopathy from the Philadelphia College of Osteopathic Medicine. He completed postgraduate training in Osteopathic affiliated hospitals in Washington State. He is certified by the National Board of Osteopathic Examiners, the American Society of Addiction Medicine, and the Medical Review Officer Certification Council.

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