Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:



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

CPT Codes:

82542 – Column includes mass spectometry, if performed, none drug analyte(s) not elsewhere specified, qualitative or quantitative, each specimen

Test Includes:

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


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 (MML Test: SLO)

Phone Numbers:

MIN Lab: 612-813-6580

STP Lab: 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. Get special tube from the laboratory.


Specimen Type:



Green top (Sodium heparin) tube

Draw Volume:

3 mL (Minimum: 0.6 mL) blood

Processed Volume:

1 mL (Minimum: 0.2 mL) plasma


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 sodium heparin or EDTA; mislabeled or unlabeled specimens


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:



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


Gas Chromatography/Mass Spectrometry (GC/MS)


Mayo Medical Laboratories Web Page (March 2012)


1/28/16: CPT update.

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