Lab Dept:

Chemistry

Test Name:

7-DEHYDROCHOLESTEROL

General Information

Lab Order Codes:

7DEH

Synonyms:

Smith-Lemli-Opitz Screen, RSH syndrome, 8-dehydrocholesterol

CPT Codes:

82541 – Column chromatography/mass spectometry, analyte not elsewhere specified; single stationary and mobile phase

Test Includes:

7-dehydrocholesterol level reported as positive or negative. Quantitative results are provided when positive.

Logistics

Test Indications:

Useful in diagnosing Smith-Lemli-Opitz (SLO) Syndrome (3 beta-hydroxysterol-delta 7-reductase deficiency).

Lab Testing Sections:

Chemistry – Sendouts

Referred to:

Mayo Medical Laboratories (Test# 81595)

Phone Numbers:

Minneapolis:

Saint Paul:

612-813-6580

651-220-6550

Test Availability:

Daily, 24 hours

Turnaround Time:

Varies, test performed 1 day per week (2 - 8 days)

Special Instructions:

See Patient Preparation

Specimen

Specimen Type:

Blood

Container:

Green top (Lithium heparin) tube

Draw Volume:

3.0 mL blood

Processed Volume:

1.0 mL (Minimum: 0.2 mL) plasma

Collection:

Routine venipuncture. Mix specimen thoroughly by gentle inversion.

Special Processing:

Lab Staff: Centrifuge immediately after collection, separate and freeze plasma. Store and ship frozen in a plastic vial. Forward promptly.

Patient Preparation:

4 or more hour fasting specimen preferred (infants before next feeding).

Sample Rejection:

Warm specimens, anticoagulants other than heparin or EDTA, mislabeled or unlabeled specimens

Interpretive

Reference Range:

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.

Critical Values:

N/A

Limitations:

The enzymatic tests for measuring plasma cholesterol quantitate all three hydroxysterols and are unreliable for diagnosis for SLO.

Methodology:

Gas Chromatography/Mass Spectrometry (GC/MS)

References:

Mayo Medical Laboratories Web Page (February 2010)