Confirm diagnosis in at-risk fetuses or those with ultrasonographic features consistent with thanatophoric dysplasia type 1 or type 2.
- Patient Preparation
- Fetal Specimen: Two T-25 flasks at 80% confluent of cultured amniocytes. If the client is unable to culture amniocytes, this can be arranged by contacting ARUP Client Services at (800) 522-2787.
Maternal Specimen: Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B).
- Specimen Preparation
- Cultured amniocytes: Fill flasks with culture media. Transport two T-25 flasks at 80% confluent of cultured amniocytes. Backup cultures must be retained at the client's institution until testing is complete.
Maternal Specimen: Transport 3 mL whole blood.
- Storage/Transport Temperature
- Cultured amniocytes: CRITICAL ROOM TEMPERATURE. Must be received within 48 hours of shipment due to lability of cells.
Maternal Specimen: Room temperature. Ship with the fetal specimen.
- Unacceptable Conditions
- Maternal sample is recommended for proper test interpretation; order Maternal Cell Contamination. Patient History Form is available on the ARUP Web site or by contacting ARUP Client Services.
- Fetal: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable
Maternal: Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable
Characteristics: Micromelia, macrocephaly, short ribs and a narrow thorax; TD I has bowed femurs and TD II has straight femurs and a cloverleaf skull; death usually occurs from respiratory insufficiency within hours or days of birth.
Incidence: 1 in 20,000 to 50,000 births.
Inheritance: Autosomal dominant; arising from a de novo mutation.
Cause: Fibroblast growth factor receptor 3 (FGFR3) gene mutations.
Mutations tested: c.742C>T (R248C), c.746C>G (S249C), c.1108G>T (G370C), c.1111A>T (S371C), c.1118A>G (Y373C), c.2419T>G (X807G), c.2419T>A (X807R), c.2420G>T (X807L), c.2420G>C (X807S), c.2421A>T (X807C), c.2421A>C (X807C) and c.2421A>G (X807W) for TD I and c.1948A>G (K650E) for TD II.
Clinical Sensitivity and Specificity: 99 percent.
Methodology: Polymerase chain reaction (PCR) and single nucleotide extension followed by capillary electrophoresis.
Analytic Specificity and Sensitivity: 99 percent.
Limitations: Mutations other than those targeted in FGFR3 will not be detected; analytic sensitivity may be compromised by rare primer site mutations. Diagnostic errors can occur due to rare sequence variations.
For quality assurance purposes, ARUP Laboratories will confirm the above result at no charge following delivery. Order Confirmation of Fetal Testing and include a copy of the original fetal report (or the mother's name and date of birth) with the test submission. Please contact an ARUP genetic counselor at (800) 242-2787 extension 2141 prior to specimen submission.
This test is performed pursuant to an agreement with Roche Molecular Systems, Inc.
|Component Test Code*||Component Chart Name||LOINC|
|0050548||Maternal Contamination Study Fetal Spec||31208-2|
|0050612||Maternal Contam Study, Maternal Spec||31208-2|
|0051488||Thanatophoric Dysplasia I/II, Fetal Spec|
|0051507||Thanatophoric Dysplasia I/II|
- Fetal Thanatophoric dysplasia fetal mutation assay
- FGFR3 fetal mutation assay