Our Providers

Karen Rendt-Zagar, MD

Karen E. Zagar, MD is a native of Pennsylvania, where she attended college (majoring in mathematics and chemistry at Clarion State College) and attended medical school (University of Pennsylvania in Philadelphia). She remained at the Hospital of the University of Pennsylvania for her internship and residency in Internal Medicine. She did her fellowship in Rheumatology at Duke University in Durham, North Carolina.

Dr Zagar joined our staff in 2005.  Prior to that, she spent six years on the staff of the Department of Rheumatic and Immunologic Diseases at the Cleveland Clinic Foundation in Cleveland, Ohio. There she served as the Fellowship Education Program Director to train physicians specializing in Rheumatology. She was also a member of the Center for Vasculitis Care and Research, headed by Dr. Gary Hoffman, and has participated in numerous clinical trials related to osteoarthritis, rheumatoid arthritis, and vasculitis.

Dr. Zagar is board certified in both Internal Medicine and Rheumatology, and she is a fellow in the American College of Rheumatology. Dr Zagar is currently Principal Investigator for all research trials and studies performed at Arthritis Center.

Dr. Zagar and her family enjoy numerous outdoor activities, particularly sailing, biking, and gardening. She also plays flute and classical piano.

Tatiana Nagibina, MD

Dr. Nagibina received her medical degree from Minsk State Medical Institute (former USSR). She completed her internship and residence in Internal medicine at The Chicago Medical School as well as fellowship in Rheumatology at the University of Illinois at Chicago.

Before joining our staff in 2011, Dr. Nagibina spent 10 years serving patients in Pinellas County providing Rheumatological care.

Dr. Nagibina is board certified in Internal medicine and Rheumatology and she is a fellow of the American College of Rheumatology.

Dr. Nagibina enjoys travel, theater, and museums.

Tatyana Korableva, PA-C

Tatyana is a nationally certified Physician Assistant with 10 years of experience in Rheumatology who obtained her Master of Clinical Medical Science degree in Physician Assistant Studies from Barry University in St. Petersburg, Florida, in 2011. She is licensed by the state of Florida and is a member of the Florida Society of Rheumatology, Florida Academy of Physician Assistants and the International Society for Clinical Densitometry.

Before attending Barry University, Tatyana attended the University of South Florida, where she obtained her Bachelor of Biomedical Science degree. She worked as an Ophthalmic Assistant in St. Petersburg, Florida for two years, Bay Area Arthritis & Osteoporosis for the following 10 years until most recently joining the Arthritis Center in October of 2021.

As a Physician Assistant Tatyana provides care in all aspects of Rheumatology with special interest in Osteoporosis treatment and prevention.

Tatyana resides in Lutz with her husband and two children and enjoys spending her free time with family and friends.

Dr Bianshly Rivera

Dr. Rivera will be joining our staff  October 17, 2022. She completed her undergraduate studies in cellular and molecular biology and obtained her medical degree from the University of Puerto Rico. During this time, she was participating in research studies on metabolic syndrome in women, which is one of her big interests. Dr. Rivera moved to Florida to complete an Internal Medicine residency at the University of South Florida (USF). She finished her Endocrinology, Diabetes, and Metabolism fellowship at USF-affiliated hospitals Tampa General Hospital, James A. Hailey Veterans Hospital, and Moffitt Cancer Center. During her training, she participated in projects related to diabetes mellitus, quality improvement, and patient safety, and presented her work at national endocrinology conferences.

Dr. Rivera is board certified in Internal Medicine and board eligible in Endocrinology, Diabetes, and Metabolism. She is particularly interested in metabolic health, obesity, diabetes mellitus, and autoimmune thyroid disease.

During her free time, she enjoys exercising, cooking healthy recipes, going to the beach, spending time with her two dogs, and shopping for new plants.

E. Markus Klaus, M.D.

Drawing on a wealth of International and North American training and experiences, Dr. Klaus is committed to a caring and compassionate approach to finding your most suitable management path to arthritis health! Born in Nurnberg, Germany, Dr. Klaus was raised in South Africa and called beautiful Camps Bay, nestled at the foothill of Table Mountain, his home. Dr. Klaus’ medical journey started at the University of Stellenbosch, where he obtained the six-year M.B.Ch.B, Bachelor of Medicine/Bachelor in Surgery degree in 2000. He gained further experience by completing two years of intensive Internship and Community Service training in Bethlehem in the eastern Free State Province, South.

Newly married to his beautiful wife, Gerdi, their international call started by moving to the Peace Valley of northern beautiful British Columbia, Canada. It was in Fort. St. John that Dr. Klaus served four years as a full-time rural Family Practitioner caring for his patients in private practice while working in the medical/surgical, OR, maternity ward, and busy ER department. He completed the Canadian Evaluating Exam of the Medical Council of Canada (2003), the Licentiate of the Medical Council of Canada (LMCCI) (2004), and LMCCII (2005). However, his growing interest in Internal Medicine called him back to South Africa, where he was privileged to study Internal Medicine under the guidance of many esteemed clinicians at the University of the Free State in Bloemfontein, South Africa.

This sparked an interest in Rheumatology and another trans-Atlantic journey for Dr. Klaus and his family back to Canada to Halifax, in the maritime province of Nova Scotia. Dr. Klaus completed his Residency in Adult Rheumatology at the prestigious Dalhousie University and obtained The Royal College of Physicians and Surgeons of Canada in Internal Medicine (2012) and the Royal College of Physicians and Surgeons of Canada in Adult Rheumatology (2013). He opened a private practice in Nova Scotia. He later moved back to British Columbia, where he initially worked in Internal Medicine in the ICU and Medical wards, but later dedicated his attention to opening a new rheumatology clinic in Chilliwack in the Eastern Fraser Valley.

Dr. Klaus worked as a solo adult rheumatologist for more than eight years and served a large clinic of patients with autoimmune, inflammatory autoimmune arthritic conditions with the help of two registered nurses. Dr. Klaus completed his American Board of Internal Medicine (ABIM) (2021), followed by the USMLE United States Medical Licensing Examinations (2022) and Special Purpose Examination (SPEX) Federation of State Medical Boards (2022). He moved with his family to Palm Harbor, Florida late 2022 and joined the staff of the Arthritis and Diabetes Center in January 2023. Dr. Klaus is particularly interested in caring for patients with inflammatory arthritis, including rheumatoid and psoriatic arthritis, ankylosing spondylitis, osteoporosis, lupus, and connective tissue diseases. During his free time, you will find Dr. Klaus enjoying the beautiful Floridian beaches with his wife, encouraging his two daughters in their XC, track, and field competitions (high school and NCAA1-level), or trying to perfect the art of Spätzle or a South African braai!