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Lab Dept:
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Chemistry
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Test Name:
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7-DEHYDROCHOLESTEROL
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General Information
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Lab Order Codes:
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7DEH
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Synonyms:
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Smith-Lemli-Opitz Screen, RSH syndrome, 8-dehydrocholesterol
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CPT Codes:
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82541 – Column chromatography/mass spectometry, analyte not elsewhere specified; single stationary and mobile phase
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Test Includes:
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7-dehydrocholesterol level reported as positive or negative. Quantitative results are provided when positive.
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Logistics
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Test Indications:
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Useful in diagnosing Smith-Lemli-Opitz (SLO) Syndrome (3 beta-hydroxysterol-delta 7-reductase deficiency).
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Lab Testing Sections:
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Chemistry – Sendouts
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Referred to:
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Mayo Medical Laboratories (Test# 81595)
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Phone Numbers:
Minneapolis:
Saint Paul:
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612-813-6580
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651-220-6550
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Test Availability:
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Daily, 24 hours
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Turnaround Time:
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Varies, test performed 1 day per week (2 - 8 days)
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Special Instructions:
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See Patient Preparation. Get special tube from the laboratory.
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Specimen
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Specimen Type:
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Blood
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Container:
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Green top (Sodium heparin) tube
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Draw Volume:
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3 mL blood
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Processed Volume:
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1 mL (Minimum: 0.2 mL) plasma
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Collection:
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Routine venipuncture. Mix specimen thoroughly by gentle inversion.
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Special Processing:
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Lab Staff: Centrifuge immediately after collection, separate and freeze plasma. Store and ship frozen in a plastic vial. Forward promptly.
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Patient Preparation:
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4 or more hour fasting specimen preferred (infants before next feeding).
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Sample Rejection:
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Warm specimens, anticoagulants other than sodium heparin or EDTA, mislabeled or unlabeled specimens
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Interpretive
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Reference Range:
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Negative (if positive, quantitative results are provided)
Interpretation: Elevated plasma concentrations of 7- and 8-DHC are highly suggestive of a biochemical diagnosis of 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.
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Critical Values:
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N/A
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Limitations:
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The enzymatic tests for measuring plasma cholesterol quantitate all three hydroxysterols and are unreliable for diagnosis for SLO.
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Methodology:
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Gas Chromatography/Mass Spectrometry (GC/MS)
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References:
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Mayo Medical Laboratories Web Page (March 2012)
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