|
|
Lab Dept:
|
Anatomic Pathology
|
Test Name:
|
X-LINKED HYPOPHOSPHATEMIA (PHEX) DELETION/DUPLICATION
|
General Information
|
Lab Order Codes:
|
PHEXF
|
Synonyms:
|
Hypophosphatemic rickets; Vitamin D-resistant rickets
|
CPT Codes:
|
81479 – Molecular Pathology Unlisted procedure
88271 x10 – Molecular cytogenetics, DNA probe, each
|
Test Includes:
|
PHEX gene sequencing and ExonArrayDx del/dup testing.
|
Logistics
|
Test Indications:
|
Use to confirm the clinical diagnosis; differentiate between X-linked and dominant forms of the disease; determine the appropriate therapeutic approach.
X-linked hypophosphatemia is the most common form of inherited rickets. Affected individuals have hypophosphatemia due to decrease renal tubular serum inorganic phosphorous reabsorbtion. It is resistant to treatment with Vitamin D. The disorder includes short stature, bowing of the lower limbs, poor dental development and extraskeletal ossification. Occasionally, spinal cord compression is present. As an X-linked dominant trait, this disorder affects both males and female. The disease is equally severe in young boys and girls, although adult males may be more severel affected than adult females. A less common form of dominant hypophosphatemia that is phenotypically similar to the X-linked form is due to gain-of-function mutation in the autosomal FGF23 gene.
|
Lab Testing Sections:
|
Anatomic Pathology – Sendouts
|
Referred to:
|
GeneDx: Test #1861E
|
Phone Numbers:
|
MIN Lab: 612-813-6280
|
STP Lab: 651-220-6550
|
Test Availability:
|
Daily, 24 hours
|
Turnaround Time:
|
Results are reported in 6-8 weeks
|
Special Instructions:
|
A complete GeneDx request form is required (select test 1861E under Hereditary rickets section). Please submit completed request form with the specimen to the laboratory.
|
Specimen
|
Specimen Type:
|
Whole blood
|
Container:
|
Lavender top (EDTA) tube
|
Draw Volume:
|
3 mL (Minimum: 1 mL) blood
|
Processed Volume:
|
Same as Draw Volume
|
Collection:
|
Routine venipuncture
|
Special Processing:
|
Lab Staff: Do Not Centrifuge. Blood specimen should remain in the original collection container. Store and ship blood specimens at refrigerated temperature.
|
Patient Preparation:
|
None
|
Sample Rejection:
|
Mislabeled or unlabeled specimens
|
Interpretive
|
Reference Range:
|
Interpretive report
|
Critical Values:
|
N/A
|
Limitations:
|
Multiple partial gene deletions have been reported in PHEX, which would not be detectable in carrier females by gene sequencing. Therefore, GeneDX performs deletion/duplication analysis in females concurrently with sequencing to evaluate for a whole or partial gene deletion in PHEX.
|
Methodology:
|
Bi-directional Sequence analysis and ExonArrayDx
|
References:
|
GeneDx webpage: http://www.genedx.com/services/dis_hrd.php
|
Updates:
|
2/11/2013: CPT update
|
