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Test Name:
Smith-Lemli-Opitz Screen, Plasma

• SBMF No:
  42157
• Performance Lab Name:
  Mayo Medical Laboratories
• Test Mnemonic:
  SLO
• ABN:
  Required – Not FDA-Approved
• CPT Code:
  82541
• LOINC Code:
  19146-0
• Ref Lab Test No:
  81595
• Also Known As:
  7-Dehydrocholesterol
  7-Dehydrocholesterol Reductase Deficiency
  8-Dehydrocholesterol
  RSH syndrome
  SLO
• Spec Type:
  Plasma
• Spec Container:
  Green top (heparin) or lavender top (EDTA) tube
• Pref Vol:
  1.0 mL
• Min Vol:
  0.2 mL
• Fasting:
  Yes
• Patient Prep:
  Patient should be fasting (12 hours or more, infants just before next feeding)
• Spec Collect:
  Routine venipuncture
• Spec Process:
  Promptly centrifuge 15 minutes
  Immediately transfer plasma to separate plastic tube and freeze
• Spec Store Transport:
  Frozen
• Spec Reject:
  Specimens other than plasma
  Anticoagulants other than sodium heparin, lithium heparin, or EDTA
  Non-frozen or thawed sample
• Spec Remarks:
  Separate plasma from cells and freeze within 45 minutes of collection
• Methodology:
  Gas Chromatography/Mass Spectrometry (GC/MS)
• Use:
  Diagnosis of Smith-Lemli-Opitz syndrome (7-dehydrocholesterol reductase deficiency)
• Clinical Significance:
  

  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 (7-dehydrocholesterol reductase deficiency) is an autosomal recessive disorder characterized by markedly increased plasma concentrations of 7-dehydrocholesterol (7-DHC) and 8-DHC levels. Severity ranges from mild to severe. Clinical features include microcephaly, growth retardation, developmental delay, dysmorphic facial features, limb abnormalities (especially syndactyly and polydactyly of the toes), and heart and kidney malfunctions. The estimated incidence is between 1:10,000 and 1:60,000.

  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.

• Reference Range:
  

  Negative (reported as positive or negative)
  Quantitative results are provided when positive

  Interpretive Data:
  Elevated plasma concentrations of 7- 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:
  The enzymatic tests for measuring plasma cholesterol quantitate all 3 hydroxysterols and are unreliable for diagnosis for Smith-Lemli-Opitz.

• Additional Test Info:
  

  This test was developed and its performance characteristics determined by Laboratory Medicine and Pathology, Mayo Clinic. This test has not been cleared or approved by the U.S. Food and Drug Administration.

  Reference:
  "Smith-Lemli-Opitz Screen, Plasma." 2011 Online Test Catalog, Mayo Medical Laboratories, 2011. Web. 30 July 2011 <http://www.mayomedicallaboratories.com/test-catalog/Overview/81595>

• Day Run:
  Sets up 1 day a week
• Time Reported:
  3-9 days
• Test Type:
  CHEMISTRY