Diagnostic fetal testing for pregnancies suspected to be affected with Smith-Lemli-Opitz syndrome (SLOS).
- Patient Preparation
- Fetal Specimen: Two T-25 flasks at 80 percent confluent culture of amniocytes. If the client is unable to culture amniocytes, this can be arranged by contacting ARUP Client Services at (800) 522-2787.
Maternal Whole Blood: Lavender (K2EDTA), Lavender (K3EDTA), Pink (K2EDTA), or Yellow (ACD Solution A or B).
- Specimen Preparation
- Cultured Amniocytes: Fill flask with culture media. Transport two T-25 flasks at 80 percent confluent of culture amniocytes filled with culture media.
Maternal Whole Blood: Transport 3 mL whole blood (Min: 1mL)
- Storage/Transport Temperature
- Cultured Amniocytes: CRITICAL ROOM TEMPERATURE. Must be received within 48 hours of shipment due to liability of cells.
Maternal Whole Blood: Room temperature.
- Unacceptable Conditions
- Maternal sample is recommended for proper test interpretation.
- Fetal Specimen: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable
Maternal Whole Blood: Ambient: 72 hours; Refrigerated: 1week; Frozen: Unacceptable
Characteristics: Smith-Lemli-Opitz syndrome (SLOS) is caused by mutations in the DHCR7 gene that disrupt the final step of cholesterol biosynthesis. Affected individuals typically have elevated serum concentration of 7-dehydrocholesterol (7-DHC). Characteristic findings include growth deficiency, postaxial polydactyly, 2-3 toe
syndactyly, intellectual disability, cardiac defects, feeding difficulty, congenital cataracts, sensorineural hearing loss, and characteristic facial features. Males with SLOS may have genitourinary anomalies such as hypospadias, cryptorchidism or undermasculinization of the external genitalia.
Incidence: 1 in 10,000-1 in 60,000 live births.
Inheritance: Autosomal recessive.
Cause: Pathogenic germline mutations in the DHCR7 gene.
Clinical Sensitivity: 96 percent.
Methodology: Bidirectional sequencing of the entire DHCR7 coding region and intron/exon boundaries.
Analytical Sensitivity and Specificity: Greater than 99 percent.
Limitations: Diagnostic errors can occur due to rare sequence variations. Regulatory region mutations, deep intronic mutations, mutations in non-coding exons 1-2, and large deletion/duplications will not be detected. Mutations in genes other than DHCR7 are not evaluated.
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.
Counseling and informed consent are recommended for genetic testing. Consent forms are available online at www.aruplab.com.
|Component Test Code*||Component Chart Name||LOINC|
|0050548||Maternal Contamination Study Fetal Spec||31208-2|
|0050612||Maternal Contam Study, Maternal Spec||31208-2|
|2011705||SLOS (DHCR7) Seq FE - Specimen||31208-2|
|2011706||SLOS (DHCR7) Seq FE - Interpretation||55195-2|