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Common Test-Ordering Errors
Part 1: Misordered Tests

1,25-Dihydroxyvitamin D
PTH-related Peptide
Uroporphyrinogen III Synthase

Required Specimen Volumes

Slide 13

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.

Required Specimen Volumes


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