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HelpOrder Code CTXP Cerebrotendinous Xanthomatosis, Plasma
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 HSMP / Hepatosplenomegaly Panel, Plasma. If this test (CTXP) is ordered with either GPSYP / Glucopsychosine, Plasma or OXNP / Oxysterols, Plasma, the individual tests will be canceled and HSMP ordered.
Specimen Required
Supplies: Sarstedt Aliquot Tube, 5 mL (T914)
Collection Container/Tube:
Preferred: Lavender top (EDTA)
Acceptable: Green top (sodium heparin, lithium heparin), yellow top (ACD B)
Submission Container/Tube: Plastic vial
Specimen Volume: 0.3 mL
Collection Instructions:
1. Centrifuge at 4° C if possible
2. Aliquot plasma into a plastic vial. Do not disturb or transfer the buffy coat layer.
3. Send frozen.
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) using plasma specimens
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, PSpecimen Type
PlasmaSpecimen Minimum Volume
0.25 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Plasma | Frozen | 65 days |
Reject Due To
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Reference Values
7-Alpha-hydroxy-4-cholesten-3-one (7a-C4)
Cutoff: ≤0.300 nmol/mL
7-Alpha,12-alpha-dihydroxycholest-4-en-3-one (7a12aC4)
Cutoff: ≤0.100 nmol/mL
Method Description
Internal standard is added to an aliquot of plasma which is then subjected to protein precipitation. Following centrifugation, the supernatant 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, Thursday
Performing Laboratory
Mayo Clinic Laboratories in Rochester
CPT Code Information
82542