Ordering Recommendation

Confirm diagnosis in at-risk fetuses or those with ultrasonographic features consistent with thanatophoric dysplasia type 1 or type 2.

Mnemonic
TD PAN FE
Methodology

Polymerase Chain Reaction/Fragment Analysis

Performed

Sun-Sat

Reported

3-7 days

New York DOH Approval Status
This test is New York DOH approved.
Specimen Required
Patient Preparation
Collect

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

Fetal Specimen: 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
Remarks

Maternal sample is recommended for proper test interpretation. Order Maternal Cell Contamination, Maternal Specimen. This can be arranged by contacting ARUP genetic counselors at (800) 242-2787 ext. 2141. Patient History Form is available on the ARUP Web site or by contacting ARUP Client Services.

Stability

Fetal Specimen: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable
Maternal Specimen:
Ambient: 72 hours; Refrigerated: 1 week; Frozen: Unacceptable

Reference Interval
Interpretive Data

Background information for Thanatophoric Dysplasia, Types 1 and 2 (FGFR3) 13 Mutations, Fetal
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.

Compliance Category

Laboratory Developed Test (LDT)

Note
Hotline History
N/A
CPT Codes

81479; 81265 Fetal Cell Contamination (FCC)

Components
Component Test Code* Component Chart Name LOINC
0050548 Maternal Contamination Study Fetal Spec 59266-7
0050612 Maternal Contam Study, Maternal Spec 31208-2
0051488 Thanatophoric Dysplasia I/II, Fetal Spec 31208-2
0051507 Thanatophoric Dysplasia I/II 75391-3
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • Fetal Thanatophoric dysplasia fetal mutation assay
  • FGFR3 fetal mutation assay
  • TD
Thanatophoric Dysplasia, Types 1 and 2 (FGFR3) 13 Mutations, Fetal