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.
Test Details
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Discipline:
Biochemistry
Biochemistry
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Specimen Container Adult:
Lithium heparin plasma
Lithium heparin plasma
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Specimen Container Paediatric:
Lithium heparin plasma
Lithium heparin plasma
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Minimum Volume Adult:
2 mL blood, 1 mL plasma
2 mL blood, 1 mL plasma
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Minimum Volume Paediatric:
1 mL blood, 0.5 mL plasma
1 mL blood, 0.5 mL plasma
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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...
Read MoreProtect 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.
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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...
Read MorePatients 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...
Read MoreReference 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.
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Routine Contact Name:
Duty Biochemist
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Routine Telephone:
Freeman: 0191 244 8889
RVI: 0191 282 9719
Freeman: 0191 244 8889
RVI: 0191 282 9719
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Routine Email:
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Specialist Test:
Yes
Yes
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Specialist Contact Name:
Metabolic Clinical Scientist
Metabolic Clinical Scientist
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Specialist Telephone:
0191 282 9685 (Consultant Clinical Scientist)
0191 282 0334 (Metabolic Laboratory)
0191 282 9685 (Consultant Clinical Scientist)
0191 282 0334 (Metabolic Laboratory)
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Specialist Email: