Test Id : SLO
Smith-Lemli-Opitz Screen, Plasma
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosing Smith-Lemli-Opitz syndrome (7-dehydrocholesterol reductase deficiency)
Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request
Smith-Lemli-Opitz syndrome (SLO) is a multiple congenital anomaly disorder caused by defective cholesterol biosynthesis due to deficiency of the enzyme 7-dehydrocholesterol (7-DHC) reductase.
Clinical variability even within families has been noted and severity of SLO ranges from severe to mild.
Elevated plasma concentrations of 7-DHC and 8-dehydrocholesterol are highly suggestive of a biochemical diagnosis of SLO.
Method Name
A short description of the method used to perform the test
Gas Chromatography Mass Spectrometry (GC-MS)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
7-Dehydrocholesterol Reductase Deficiency
8-Dehydrocholesterol
RSH Syndrome
Smith Lemli Opitz (SLO)
7DHC
7-DHC
8DHC
8-DHC
Specimen Type
Describes the specimen type validated for testing
Plasma
Necessary Information
Biochemical Genetics Patient Information (T602) is recommended, but not required, to be filled out and sent with the specimen to aid in the interpretation of test results.
Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
Collection Container/Tube:
Preferred: Green top (sodium or lithium heparin)
Acceptable: Lavender top (EDTA), pearl white top (EDTA plasma gel), yellow top (ACD solution A or B)
Submission Container/Tube: Plastic vial
Specimen Volume: 0.5 mL
Collection Instructions:
1. Centrifuge and aliquot plasma into plastic vial.
2. Send plasma frozen.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
Forms
1. Biochemical Genetics Patient Information (T602)
2. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
0.1 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma | Frozen (preferred) | 92 days | |
| Ambient | 14 days | ||
| Refrigerated | 28 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
Diagnosing Smith-Lemli-Opitz syndrome (7-dehydrocholesterol reductase deficiency)
Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request
Smith-Lemli-Opitz syndrome (SLO) is a multiple congenital anomaly disorder caused by defective cholesterol biosynthesis due to deficiency of the enzyme 7-dehydrocholesterol (7-DHC) reductase.
Clinical variability even within families has been noted and severity of SLO ranges from severe to mild.
Elevated plasma concentrations of 7-DHC and 8-dehydrocholesterol are highly suggestive of a biochemical diagnosis of SLO.
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Cholesterol plays an essential role in many cellular and developmental processes. In addition to its role as a membrane lipid, it is the precursor to numerous molecules that play important roles in cell growth and differentiation, protein glycosylation, and signaling pathways. The biosynthesis of cholesterol and its subsequent conversion to other essential compounds is complex, involving a number of intermediates and enzymes. Disorders that result from a deficiency of these enzymes lead to an accumulation of specific intermediates and inhibit the formation of important biomolecules. Clinical findings common to cholesterol biosynthesis disorders include congenital skeletal malformations, dysmorphic facial features, psychomotor retardation, and failure to thrive.
Smith-Lemli-Opitz syndrome (SLO) is an autosomal recessive disorder caused by variants in the DHCR7 gene leading to a deficiency of the 7-dehydrocholesterol reductase enzyme. It is characterized biochemically by markedly increased plasma concentrations of 7-dehydrocholesterol and 8-dehydrocholesterol levels. Clinical features can include microcephaly, growth retardation, developmental delay, dysmorphic facial features, cleft palate, limb abnormalities (especially 2-3 syndactyly of the toes and postaxial polydactyly), and heart and kidney malformations. However, the clinical spectrum ranges from mild to severe with some mildly affected individuals presenting with only 2-3 toe syndactyly and mild cognitive impairment. The reported incidence is between 1 in 10,000 and 1 in 60,000, but it may be more prevalent due to underdiagnoses of mildly affected individuals.
Other disorders of cholesterol biosynthesis, including desmosterolosis (desmosterol reductase deficiency) and sitosterolemia, may present with similar manifestations. These disorders can be detected biochemically by performing a quantitative profile of plasma sterols (STER / Sterols, Plasma).
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
7-DEHYDROCHOLESTEROL
< or =2.0 mg/L
8-DEHYDROCHOLESTEROL
< or =0.3 mg/L
Interpretation
Provides information to assist in interpretation of the test results
Elevated plasma concentrations of 7-dehydrocholesterol (7-DHC) and 8-dehydrocholesterol are highly suggestive of a biochemical diagnosis of Smith-Lemli-Opitz (SLO) syndrome.
Mild elevations of these cholesterol precursors can be detected in patients with hypercholesterolemia and patients treated with some antipsychotic or antidepressant medications, including haloperidol, aripiprazole, and trazodone. However, the 7-DHC to cholesterol ratio is typically elevated only in patients with SLO syndrome.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
On very rare occasions, 7-dehydrocholesterol (7-DHC) is not elevated in patients with Smith-Lemli-Opitz (SLO) syndrome.
Cholesterol screening tests are unreliable for diagnosis for SLO syndrome.
Some antipsychotic or antidepressant medications, such as aripiprazole and trazodone cause false elevations in 7-DHC.
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Donoghue SE, Pitt JJ, Boneh A, White SM. Smith-Lemli-Opitz syndrome: clinical and biochemical correlates. J Pediatr Endocrinol Metab. 2018;31(4):451-459
2. Nowaczyk MJM, Wassif CA. Smith-Lemli-Opitz syndrome. In: Adam MP, Mirzaa GM, Pagon RA, et al., eds. GeneReviews [Internet]. University of Washington, Seattle; 1998. Updated January 30, 2020.Accesses November 02, 2023. Available at www.ncbi.nlm.nih.gov/books/NBK1143/
3. Hall P, Michels V, Gavrilov D, et al. Aripiprazole and trazodone cause elevations of 7-dehydrocholesterol in the absence of Smith-Lemli-Opitz syndrome. Mol Genet Metab. 2013;110(1-2):176-178
4. Genaro-Mattos TC, Tallman KA, Allen LB, et al. Dichlorophenyl piperazines, including a recently-approved atypical antipsychotic, are potent inhibitors of DHCR7, the last enzyme in cholesterol biosynthesis. Toxicol Appl Pharmacol. 2018;349:21-28. doi:10.1016/j.taap.2018.04.029
Method Description
Describes how the test is performed and provides a method-specific reference
The plasma specimen is hydrolyzed and then extracted followed by evaporation to dryness under nitrogen. The sterols are derivatized and then analyzed using selected ion-monitoring electron impact gas chromatography mass spectrometry to quantitate 7-dehydrocholesterol and 8-dehydrocholesterol.(Unpublished Mayo method)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Tuesday, Friday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.
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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
82542
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| SLO | Smith-Lemli-Opitz Scrn, P | 73852-6 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| 29974 | Reviewed By | 18771-6 |
| 29972 | Interpretation | 59462-2 |
| 610625 | 7-Dehydrocholesterol | 33275-9 |
| 610626 | 8-Dehydrocholesterol | 34671-8 |