Which biochemical tests should be ordered for a patient one year after Roux-en-Y gastric bypass?

Which biochemical tests should be ordered for a patient one year after Roux-en-Y gastric bypass?

• A. Niacin, vitamin B12, and zinc
• B. Calcium, magnesium, and vitamin A
• C. 25-Hydroxy Vitamin D, Intact PTH, and Vitamin B12
• D. Intact PTH, 1,25-dihydroxy Vitamin D, and thiamin

Answer: (C)

After Roux-en-Y gastric bypass, the altered gut anatomy leads to malabsorption of several nutrients, so monitoring focuses on nutrients most commonly affected and tied to long-term health, especially bone health and vitamin B12 status. Measuring 25-hydroxy vitamin D is the best way to assess vitamin D stores in the body because it reflects overall status from all sources, not just the active form at a single moment. Intact parathyroid hormone provides information about the body's response to calcium and vitamin D status; a rise in PTH can indicate secondary hyperparathyroidism due to deficiency and helps gauge bone turnover risk. Vitamin B12 is particularly important to monitor after gastric bypass because reduced gastric acid and bypassed absorption sites increase the risk of B12 deficiency over time, which can lead to neurologic and hematologic problems if not identified early. Other options mix nutrients that are important but either are less critical to screen routinely at this one-year mark or are not as reliable for initial assessment. For example, calcium and magnesium levels alone don’t give the full picture of bone health and may miss early issues; 1,25-dihydroxy vitamin D is the active form and can be normal despite deficiency, so it isn’t the best screening marker; thiamin deficiency tends to present earlier in the postoperative period and is driven by specific risk factors rather than routine one-year screening.

After Roux-en-Y gastric bypass, the altered gut anatomy leads to malabsorption of several nutrients, so monitoring focuses on nutrients most commonly affected and tied to long-term health, especially bone health and vitamin B12 status. Measuring 25-hydroxy vitamin D is the best way to assess vitamin D stores in the body because it reflects overall status from all sources, not just the active form at a single moment. Intact parathyroid hormone provides information about the body's response to calcium and vitamin D status; a rise in PTH can indicate secondary hyperparathyroidism due to deficiency and helps gauge bone turnover risk. Vitamin B12 is particularly important to monitor after gastric bypass because reduced gastric acid and bypassed absorption sites increase the risk of B12 deficiency over time, which can lead to neurologic and hematologic problems if not identified early.

Other options mix nutrients that are important but either are less critical to screen routinely at this one-year mark or are not as reliable for initial assessment. For example, calcium and magnesium levels alone don’t give the full picture of bone health and may miss early issues; 1,25-dihydroxy vitamin D is the active form and can be normal despite deficiency, so it isn’t the best screening marker; thiamin deficiency tends to present earlier in the postoperative period and is driven by specific risk factors rather than routine one-year screening.