Smith-Lemli-Opitz Screen, Plasma
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Diagnosis of Smith-Lemli-Opitz syndrome (7-dehydrocholesterol reductase deficiency)
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Gas Chromatography-Mass Spectrometry (GC-MS)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Smith-Lemli-Opitz Scrn, P
7-Dehydrocholesterol Reductase Deficiency
Smith Lemli Opitz (SLO)
Smith Lemli Opitz (SLO)
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Preferred: Green top (sodium heparin)
Acceptable: Lavender top (EDTA)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
1. Fasting (12 hours or more, infants just before next feeding).
2. Spin down within 45 minutes of draw.
1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.
2. If not ordering electronically, submit a Biochemical Genetics Request Form (Supply T439) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross OK
Mild OK; Gross OK
Mild OK; Gross OK
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
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 an important role 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. In addition to an accumulation of specific intermediates, defects in this pathway may result in a deficiency of cholesterol. Clinical findings common to cholesterol biosynthesis disorders include congenital skeletal malformations, dysmorphic facial features, psychomotor retardation, and failure to thrive.
Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive disorder caused by mutations in the DHCR7 gene leading to a deficiency of the 7-dehydrocholesterol reductase enzyme. It is characterized by markedly increased plasma concentrations of 7-dehydrocholesterol (7-DHC) and 8-DHC 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. Severity of SLOS ranges from severe to mild. Some mildly affected individuals may only have 2 to 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 underdiagnosis 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.
Negative (reported as positive or negative)
Quantitative results are provided when positive.
Elevated plasma concentrations of 7-dehydrocholesterol (7-DHC) and 8-DHC are highly suggestive of a biochemical diagnosis of Smith-Lemli-Opitz (SLO).
Mild elevations of these cholesterol precursors can be detected in patients with hypercholesterolemia and patients treated with haloperidol. However, the 7-DHC to cholesterol ratio is only elevated in SLO patients.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
The enzymatic tests for measuring plasma cholesterol quantitate all 3 hydroxysterols and are unreliable for diagnosis for Smith-Lemli-Opitz.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Haas D, Kelley RI, Hoffmann GF: Defects of cholesterol biosynthesis. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K Sarafoglou. New York, McGraw-Hill Medical, 2009, pp 313-321
2. Irons M: Smith-Lemli-Opitz Syndrome. 1998 Nov 13 9 Updated 2007 Oct 240. In GeneReviews [Internet]. Edited by RA Pagon, TD Bird, CR Dolan, et al. University of Washington, Seattle, 1993. Available from URL: http://www.ncbi.nlm.nih.gov/books/NBK1143/
Method Description Describes how the test is performed and provides a method-specific reference
The plasma specimen is hydrolyzed with 2% KOH/ethanol for 1 hour at 65 degrees C. The compounds are then extracted with hexane, followed by evaporation to dryness under nitrogen. Using 50:50 50 bis-(trimethylsilyl) trifluoroacetamide (BSTFA:pyridine), the sterols are derivatized to generate trimethylsilyl ethers. The derivatized specimens are then transferred to gas chromatography (GC) sampling vials and 2 mcL are injected onto a HP-5 capillary column. Selected ion-monitoring electron impact gas chromatography-mass spectrometry is used as qualitative screening. When 7-dehydrocholesterol (7-DHC) and 8-DHC are detected in abnormal concentrations (>2 mcg/mL), quantitative analysis is performed via gas chromatography with flame ionization detection using epi-coprostanol as the internal standard.(Kelley RI: Diagnosis of Smith-Lemli-Opitz syndrome by gas chromatography/mass spectrometry of 7-dehydrocholesterol in plasma, amniotic fluid and cultured skin fibroblasts. Clin Chim Acta 1995;236:45-58)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Varies; Batched 1 time per week
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
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 The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. 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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|29970||Reason For Referral||42349-1|
|81595||Smith-Lemli-Opitz Scrn, P||In Process|