Vitamin D measured by chemiluminescent assay on the Abbott Architect
Assessment of vitamin D status is relevant in disturbances of calcium homeostasis. As 25-hydroxy vitamin D (25-OH-D) has a relatively long half-life and is the most abundant form of vitamin D, it is most often measured to assess vitamin D status. Its measurement is indicated in cases of suspected vitamin D deficiency e.g. rickets (children), osteomalacia (adults), neonatal hypocalcaemia, nutritional osteodystrophy (especially in the elderly, institutionalised and Asian populations, malabsorption (e.g. in cystic fibrosis, primary biliary cirrhosis) and in patients on long-term anticonvulsant therapy (barbiturate and phenytoin combination therapy in particular). Cases of vitamin D toxicity are rare and almost always iatrogenic in nature. In renal failure conversion of 25-OH-D to 1,25-OH-D may be inadequate, in which case measurement of calcitriol may be required.