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Order Code CTXWB Cerebrotendinous Xanthomatosis, Blood


Ordering Guidance


For assessment of bile acid malabsorption in patients with irritable bowel syndrome-diarrhea, order 7AC4 / 7AC4, Bile Acid Synthesis, Serum.

 

This test is also available as a part of a panel; see HSMWB / Hepatosplenomegaly Panel, Blood. If this test (CTXWB) is ordered with either GPSYW / Glucopsychosine, Blood or OXYWB / Oxysterols, Blood, the individual tests will be canceled and HSMWB ordered.



Specimen Required


Container/Tube:

Preferred: Lavender top (EDTA)

Acceptable: Green top (sodium heparin, lithium heparin), yellow top (ACD B)

Specimen Volume: 1 mL

Collection Instructions: Send whole blood in original vial. Do not aliquot.


Forms

1. Biochemical Genetics Patient Information (T602)

2. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.

Useful For

Evaluating patients with a clinical suspicion of cerebrotendinous xanthomatosis (CTX)

 

Monitoring of individuals with CTX on chenodeoxycholic acid (CDCA) therapy

 

This test is not useful for the identification of carriers

 

This test is not useful for the evaluation of bile acid malabsorption

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)

Reporting Name

Cerebrotendinous Xanthomatosis, B

Specimen Type

Whole blood

Specimen Minimum Volume

0.25 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Refrigerated (preferred) 72 hours
  Ambient  48 hours

Reject Due To

Gross hemolysis OK
Gross lipemia OK
Gross icterus OK

Reference Values

7-ALPHA-HYDROXY-4-CHOLESTEN-3-ONE (7a-C4)

Cutoff: ≤0.750 nmol/mL

 

7-ALPHA,12-ALPHA-DIHYDROXYCHOLEST-4-en-3-ONE (7a12aC4)

Cutoff: ≤0.250 nmol/mL

Method Description

Whole blood is spotted on filter paper and dried overnight. A 3-mm dried blood spot is extracted with internal standard. The extract is subjected to liquid chromatography tandem mass spectrometry (LC-MS/MS) analysis. The MS/MS is operated in the multiple reaction monitoring positive mode to follow the precursor to product species transitions for each analyte and internal standard. The ratio of the extracted peak areas to internal standard determined by the LC-MS/MS is used to calculate the concentration of in the sample.(Unpublished Mayo method)

Day(s) Performed

Tuesday

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

82542