Serum 25-Hydroxyvitamin D Concentrations from Patient Groups at High Risk for Deficiency

Background: Deficiency of 25-hydroxyvitamin D in serum is endemic in the general population, and testing for this hormone is useful in accessing a patient9s overall health and well-being. Methods: We obtained blood from 216 hospitalized patients and outpatients divided into 4 groups thought to be at high risk of 25-hydroxyvitamin D deficiency: homeless, recreational drug abusers, psychiatric patients with limited access to the outdoors, and those infected with HIV. The 25-hydroxyvitamin D concentrations from these patients were determined with 2 different methodologies (immunoassay and mass spectrometry) and compared against 25-hydroxyvitamin D concentrations in apparently healthy controls. We hypothesized that these groups may be at higher risk for vitamin D deficiency because of poor nutrition, inadequate housing, restricted access to outdoors, or the presence of chronic disease. Results: For each of the patient groups including healthy controls, the median concentration of 25-hydroxyvitamin D was below 30 ng/mL, indicating deficiency. Comparisons between the healthy controls and the other groups were not statistically significant with either methodology, except for the homeless patients in whom a higher number of individuals had 25-hydroxyvitamin D concentrations below 20 ng/mL. Results between the 2 testing platforms demonstrated that only 52% of the specimens analyzed by immunoassay agreed within ±10% of the LC-MS/MS results, with an overall correlation coefficient to 0.920. The degree of concordance for deficiency with 2 published cutoffs of 20 and 30 ng/mL was 91% and 91%, respectively. Conclusions: Vitamin D deficiency is a common finding in all the populations studied. The Lumipulse® G vitamin D immunoassay is an alternative for detecting vitamin D deficiency.