MEDizzy - You are caring for a 72-year-old man who has been living in

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You are caring for a 72-year-old man who has been living in a nursing home for the past 3 years. He has severe chronic obstructive pulmonary disease and requires continuous oxygen at 3 L/min. He also previously had a stroke, which has left him with a right hemiparesis. His current medications include aspirin, losartan, hydrochlorothiazide, futicasone/salmeterol, tiotropium, and albuterol. His BMI is 18.5 kg/m2. You are concerned that he may have vitamin D defciency. Which of the following is the best test to determine if vitamin D defciency is present?

ExplanationVitamin D defciency is highly prevalent in the United States and is most common in older individuals who are hospitalized or institutionalized. Vitamin D defciency can occur as a result of inadequate dietary intake, decreased production in the skin, decreased intestinal absorption, accelerated losses, or impaired vitamin D activation in the liver or kidney. Clinically, vitamin D defciency in older individuals is most often silent. Often practitioners fail to consider vitamin D defciency until a patient has been diagnosed with osteoporosis or sufered a fracture. However, some individuals can experience difuse muscle and bone pain. When assessing vitamin D levels, the appropriate test is 25-hydroxyvitamin D [25(OH)D] levels. The Institute of Medicine has defned vitamin D sufciency as a level of 25(OH)D >50 nmol/L (>20 ng/L). However, in the elderly and in some disease states, higher levels may be required to maximize intestinal calcium absorption. Levels less than 37 nmol/L (15 ng/mL) are associated with a rise in parathyroid hormone levels and a fall in bone density. Vitamin D defciency may also lead to decreased intestinal absorption of calcium with resultant hypocalcemia and secondary hyperparathyroidism. As a result, there is higher bone turnover, which can be associated with an increase in alkaline phosphatase levels. In addition, elevated parathyroid hormone (PTH) stimulates renal conversion of 25(OH)D to 1,25-hydroxyvitamin D [1,25(OH)D], the activated form of vitamin D. Thus, even in the face of severe vitamin D defciency, the activated 1,25(OH)D levels may be normal and do not accurately refect vitamin D stores. Thus, 1,25(OH)D should not be used to make a diagnosis of vitamin D defciency. Although vitamin D defciency may be associated with abnormalities in PTH, alkaline phosphatase, and calcium levels, these biochemical abnormalities are seen in many other diseases and are neither sensitive nor specifc for the diagnosis of vitamin D defciency.