Common Test-Ordering Errors
Part 1: Misordered Tests

Required Specimen Volumes

April 2010

The test for 1,25-Dihydroxyvitamin D also is one of our most common “quantity not sufficient” (QNS) problems. We require 1.5 mL for 1,25-Dihydroxyvitamin D, while the preferred screening test (25-Hydroxyvitamin D), requires only 0.5 mL. While 1.5 mL may seem excessive, 1,25-Dihydroxyvitamin D concentrations are much lower than 25-Hydroxyvitamin D concentrations (1,25-Dihydroxyvitamin D is present at pg/mL levels, whereas 25-Hydroxyvitamin D is present at ng/mL levels). Therefore, more sample is necessary to measure at that lower level.

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Required Specimen Volumes

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Jump to section:

• Introduction
• Testing at Mayo Medical Laboratories
• Common Test-Ordering Errors
• Misordered Tests
• Vitamin D Assessment
• Vitamin D
• Vitamin D Assessment
• Sources of Vitamin D
• Vitamin D Pathway
• Sunlight Exposure
• Vitamin D Pathway
• Useful For
• Required Specimen Volumes
• Parathyroid Hormone (PTH)
• Porphyria Enzymes
• Conclusion
• Questions?