Newcastle Laboratories

Plasma 7-dehydrocholesterol, Desmosterol and Lathosterol

Clinical Background:

Measurement of 7-dehydrocholesterol, desmosterol and lathosterol in plasma by GC-MS is performed to investigate rare inherited metabolic disorders of cholesterol synthesis. 

Smith-Lemli-Opitz syndr...

Measurement of 7-dehydrocholesterol, desmosterol and lathosterol in plasma by GC-MS is performed to investigate rare inherited metabolic disorders of cholesterol synthesis. 

Smith-Lemli-Opitz syndrome (SLOS) is caused by deficiency of 7-dehyrocholesterol reductase and results in grossly elevated plasma 7-dehydrocholesterol.   Patients present with a range of clinical features of varying severity including characteristic dysmorphic features, syndactyly of the second and third toes, congenital heart defects and growth retardation. 

Desmosterolosis (desmosterol reductase deficiency) and lathosterolosis (sterol Δ5-desaturase deficiency) are extremely rare disorders diagnosed by finding elevated plasma desmosterol and lathosterol respectively.  Very small numbers of cases have been described which have similar clinical features to SLOS.

Measurement of total cholesterol is a poor screening test for these disorders as levels may be within age-related reference ranges.

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Test Details

  • Discipline:

    Biochemistry

    Biochemistry

  • Specimen Container Adult:

    Lithium heparin plasma

    Lithium heparin plasma

  • Specimen Container Paediatric:

    Lithium heparin plasma

    Lithium heparin plasma

  • Minimum Volume Adult:

    2 mL blood, 1 mL plasma

    2 mL blood, 1 mL plasma

  • Minimum Volume Paediatric:

    1 mL blood, 0.5 mL plasma

    1 mL blood, 0.5 mL plasma

  • Special Requirement:

    Protect from light. 

    Blood sample should be centrifuged on receipt in the laboratory and the plasma separated and frozen.

    If urgent sample analysis is required, please contact the laboratory to dis...

    Protect from light. 

    Blood sample should be centrifuged on receipt in the laboratory and the plasma separated and frozen.

    If urgent sample analysis is required, please contact the laboratory to discuss.

     

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  • Transport Requirements:

    NUTH users: send sample to the laboratory at ambient temperature, protected from light.

    External hospitals: send sample to the RVI frozen and protected from light.

    NUTH users: send sample to the laboratory at ambient temperature, protected from light.

    External hospitals: send sample to the RVI frozen and protected from light.

  • Interpretation:

    Patients with Smith-Lemli-Opitz syndrome typically have levels of 7-dehydrocholesterol over 100-fold greater than the reference range.  Significantly increased lathosterol or desmosterol is consist...

    Patients with Smith-Lemli-Opitz syndrome typically have levels of 7-dehydrocholesterol over 100-fold greater than the reference range.  Significantly increased lathosterol or desmosterol is consistent with lathosterolosis or desmosterolosis respectively.

    Measurement of the sterol/cholesterol ratio can improve the diagnostic specificity of the test.

    Exposure to light may cause degradation of sterols.

    A diagnosis of SLOS, desmosterolosis or lathosterolosis should be confirmed by gene mutation analysis.

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  • Reference Ranges:

     

    Reference Ranges for Sterols in Plasma and Serum

    Sterol

    Adults (18 years and over)

    Paediatrics (under 18 yrs)

    Units

    Cholesterol

    2500 – 7200

    1900 – 4900

    µmol/L

    7-dehydr...

     

    Reference Ranges for Sterols in Plasma and Serum

    Sterol

    Adults (18 years and over)

    Paediatrics (under 18 yrs)

    Units

    Cholesterol

    2500 – 7200

    1900 – 4900

    µmol/L

    7-dehydrocholesterol

    Less than 2.5

    Less than 1.0

    µmol/L

    Lathosterol

    Less than 12.3

    Less than 5.7

    µmol/L

    Desmosterol

    Less than 4.2

    Less than 4.3

    µmol/L

     

     

    Reference Ranges for Sterol/Cholesterol ratios

    Sterol ratio

    Adults  (18 years and over)

    Paediatrics (under 18 yrs)

    Units

    7-dehydrocholesterol/ cholesterol

    Less than 0.40

    Less than 0.40

    µmol/mmol

    Lathosterol/cholesterol

    0.25 – 2.65

    0.24 – 1.92

    µmol/mmol

    Desmosterol/cholesterol

    0.14 – 0.75

    0.22 – 1.42

    µmol/mmol

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  • Other Info:

    Serum or EDTA plasma are also acceptable, but must be protected from light.

    Serum or EDTA plasma are also acceptable, but must be protected from light.

  • Routine Contact Name:

    Duty Biochemist

  • Routine Telephone:

    Freeman: 0191 244 8889

    RVI: 0191 282 9719

    Freeman: 0191 244 8889

    RVI: 0191 282 9719

  • Routine Email:

  • Specialist Test:

    Yes

    Yes

  • Specialist Contact Name:

    Metabolic Clinical Scientist

    Metabolic Clinical Scientist

  • Specialist Telephone:

    0191 282 9685 (Consultant Clinical Scientist)

    0191 282 0334 (Metabolic Laboratory)

    0191 282 9685 (Consultant Clinical Scientist)

    0191 282 0334 (Metabolic Laboratory)

  • Specialist Email:

Availability:

Available during full access hours
Assayed monthly
Site of analysis: RVI

Turn Around:

Within 8 weeks

Send To:

Department of Blood Sciences

Level 3
Leazes Wing
Royal Victoria Infirmary
Queen Victoria Road
Newcastle upon Tyne
NE1 4LP

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