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JAMA Diagnostic Test Interpretation
July 26, 2019

Interpretation of Vitamin B12 Status After a Roux-en-Y Gastric Bypass

Author Affiliations
  • 1Southern California Permanente Medical Group, Fontana, California
JAMA. 2019;322(9):887-888. doi:10.1001/jama.2017.18945

A 37-year-old woman with a history of diabetes, hypertension, obstructive sleep apnea, depression, and Roux-en-Y gastric bypass (RYGB) 16 years prior presented to an ambulatory care clinic with fatigue, loss of appetite, and hair loss. She lost 50.8 kg from the time of the procedure to presentation, her body mass index at presentation was 23, and her preoperative comorbidities were in remission. She did not have any nausea, abdominal pain, or change in bowel habits, but her periods had been more irregular over the past 2 to 3 months and, when present, lasted for 7 to 10 days. She also noted a tingling sensation in her hands and feet. She was under some financial stress after recently losing her job, and reported drinking 2 to 6 beers within a 2-hour period on the weekends. She took a gummy multivitamin sporadically and self-reported a daily total calorie intake of less than 500 kcal and less than 20 g of protein. On physical examination, although she reported having paresthesias in her fingertips and toes, her neurological examination findings were nonfocal. She exhibited bilateral flattening of the temporalis muscle and thenar eminence. Her vital signs were normal, and serum tests were ordered (Table).