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HelpTest ID 2425D 25-Hydroxyvitamin D:24,25-Dihydroxyvitamin D Ratio, Serum
Ordering Guidance
The preferred initial test for assessing vitamin D status and most accurately reflects the body's vitamin D stores is the 25-hydroxyvitamin D test; order 25HDN / 25-Hydroxyvitamin D2 and D3, Serum.
In the presence of kidney disease or hypercalcemia, testing of 1,25-dihydroxy vitamin D may be needed to adequately assess vitamin D status; order DHVD / 1,25-Dihydroxyvitamin D, Serum.
Specimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube: Red top
Submission Container/Tube: Plastic vial
Specimen Volume: 1.7 mL Serum
Collection Instructions: Within 2 hours of collection, centrifuge and aliquot serum into a plastic vial.
Secondary ID
63416Useful For
Screening for CYP24A1 deficiency
Evaluation of parathyroid hormone-independent hypercalcemia
Evaluation of recurrent nephrolithiasis or nephrocalcinosis associated with suspected vitamin D-mediated disease
Selection of patients for confirmatory molecular testing
Specimen Type
SerumSpecimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Serum | Refrigerated (preferred) | 14 days |
| Frozen | 30 days | |
| Ambient | 7 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | Reject |
| Gross icterus | OK |
Reference Values
Interpretative commentary provided based on 25-hydroxyvitamin D (25HDN) to 24,25-dihydroxyvitamin D (24,25D) ratio result.
25HDN to 24,25D Ratio
<25: Consistent with normal CYP24A1 activity, although overlap with heterozygous carriers has been reported.
25-80: May be observed in vitamin D deficiency or heterozygous CYP24A1 variants. Correlation with clinical findings is recommended. Molecular testing may be appropriate when clinical suspicion is high.
>80: Strongly suggests markedly reduced CYP24A1 activity. Confirmatory molecular testing is recommended.
Day(s) Performed
Wednesday
Report Available
2 to 15 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
82306
82542