An Underestimation of 25-OH Vitamin D in Patients with Renal Disease by the Abbott Architect Immunoassay

To the Editor: Patients with advanced chronic kidney disease (CKD)1 typically have reduced serum 1,25-hydroxyvitamin D (1,25-OHD) concentrations due to the inability to convert inactive 25-hydroxyvitamin D (25-OHD) to active 1,25-OHD. However, decreased 1,25-OHD can also be a result of 25-OHD deficiency due to coexisting conditions, such as liver disease, intestinal malabsorption, or urinary wasting of the vitamin-bound 25-OHD binding protein. The National Kidney Foundation Kidney Disease: Improving Global Outcomes has detailed guidelines for the prevention and treatment of vitamin D insufficiency and deficiency in CKD patients. According to the guidelines, patients in CKD stages 2–4 should have …