Test Id : CTXP
Cerebrotendinous Xanthomatosis, Plasma
Useful For
Suggests clinical disorders or settings where the test may be helpful
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
A short description of the method used to perform the test
Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.
Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test
Aliases
Lists additional common names for a test, as an aid in searching
Cerebral cholesterinosis
Cerebrotendinous cholesterosis
Van Bogaert-Scherer-Epstein syndrome
Sterol 27-hydrolase deficiency
Ketosterols
7-alpha hydroxy-4-cholesten-3-one
7aC4
7-alpha,12 alpha-dihydroxycholest-4-en-3-one
12aC4
7a12aC4
7,12aC4
CTX
Specimen Type
Describes the specimen type validated for testing
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
Defines the optimal specimen required to perform the test and the preferred volume to complete testing
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 degrees C if possible
2. Aliquot plasma into a plastic vial. Do not disturb or transfer the buffy coat layer.
3. Send frozen.
Special Instructions
Library of PDFs including pertinent information and forms related to the test
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.
Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the testing laboratory. The minimum volume is sufficient for one attempt at testing.
0.25 mL
Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected
| Gross hemolysis | OK |
| Gross lipemia | OK |
| Gross icterus | OK |
Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma | Frozen | 65 days |
Useful For
Suggests clinical disorders or settings where the test may be helpful
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.
Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Cerebrotendinous xanthomatosis (CTX) is an autosomal recessive disorder of bile acid synthesis resulting from the deficiency of the mitochondrial enzyme, sterol 27-hydrolase. Sterol 27-hydrolase is an important enzyme in both the alternative and classic bile acid synthesis pathways. Consequently, patients with CTX will experience increased storage of the sterol, cholestenol, and ketosterol bile acid precursors (7-alpha-hydroxy-4-cholesten-3-one [7aC4] and 7-alpha,12-alpha–dihydroxycholest-4-en-3-one [7a12aC4]) in multiple tissues throughout the body with a resulting deficiency of the bile acid, chenodeoxycholic acid (CDCA). Cerebrotendinous xanthomatosis is caused by disease-causing variants in the CYP27A1 gene.
Patients with CTX can present with a constellation of findings, including infantile onset diarrhea, childhood onset cataracts, development of tendon/cerebral xanthomas in adolescence and early adulthood, early onset osteoporosis, as well as a broad array of neuropsychological manifestations, such as intellectual disability, dementia, psychiatric symptoms, ataxia, pyramidal signs, dystonia, and muscle weakness. Patients may occasionally present with cholestatic liver disease, which may present as jaundice, poor growth, and hepatosplenomegaly. Intrafamilial variability exists and can be substantial. Some heterozygous carriers may experience a higher incidence of cardiac disorders or gallstones; however, carriers are typically asymptomatic. Treatment with CDCA has been shown to improve both biochemical and clinical outcomes in patients with CTX. Supplementation with beta-hydroxy beta-methylglutaryl-CoA (HMG-CoA) reductase inhibitors can be used as alternative treatment alone or in combination with CDCA. Cholic acid treatment has been used in few patients showing a decrease in cholestanol levels and improvement in neurologic symptoms. The availability of effective therapy makes early diagnosis and treatment of patients with CTX essential.
The diagnostic evaluation of patients with suspected CTX may reveal abnormalities on brain magnetic resonance imaging (eg, cerebellar atrophy, decrease in volume of grey and white matter, and abnormal white matter signal) in addition to the biochemical and clinical abnormalities. The biochemical diagnosis of CTX can be confirmed by molecular genetic analysis of the CYP27A1 gene (included in CHLGP / Cholestasis Gene Panel, Varies; or order CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies and indicate the gene to be assessed).
Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
7-Alpha-hydroxy-4-cholesten-3-one (7a-C4)
Cutoff: < or =0.300 nmol/mL
7-Alpha,12-alpha-dihydroxycholest-4-en-3-one (7a12aC4)
Cutoff: < or =0.100 nmol/mL
Interpretation
Provides information to assist in interpretation of the test results
An elevation of 7-alpha-hydroxy-4-cholesten-3-one (7aC4) or 7-alpha,12-alpha-dihydroxycholest-4-en-3-one (7a12aC4) or both is strongly suggestive of cerebrotendinous xanthomatosis.
Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Patients with bile acid malabsorption or ileal resection may have elevations of 7-alpha-hydroxy-4-cholesten-3-one (7aC4).
Clinical Reference
Recommendations for in-depth reading of a clinical nature
1. Mignarri A, Magni A, Del Puppo M, et al. Evaluation of cholesterol metabolism in cerebrotendinous xanthomatosis. J Inherit Metab Dis. 2016;39(1):75-83
2. Nie S, Chen G, Cao X, Zhang Y. Cerebrotendinous xanthomatosis: a comprehensive review of pathogenesis, clinical manifestations, diagnosis, and management. Orphanet J Rare Dis. 2014;9:179
3. DeBarber AE, Luo J, Star-Weinstock M, et al. A blood test for cerebrotendinous xanthomatosis with potential for disease detection in newborns. J Lipid Res. 2014;55(1):146-154
4. Federico A, Gallus GN. Cerebrotendinous xanthomatosis. In: Adam MP, Feldman J, Mirzaa GM, et al, eds. GeneReviews[Internet]. University of Washington, Seattle; 2003. Updated November 14, 2024. Accessed December 2, 2024. Available at www.ncbi.nlm.nih.gov/books/NBK1409/
5. Lutjohann D, Stellaard F, Bjorkhem I. Levels of 7alpha-hydroxycholesterol and/or 7alpha-hydroxy-4-cholest-3-one are the optimal biochemical markers for the evaluation of treatment of cerebrotendinous xanthomatosis. J Neurol. 2020;267(2):572-573. doi:10.1007/s00415-019-09650-0
6. Mandia D, Chaussenot A, Besson G, et al. Cholic acid as a treatment for cerebrotendinous xanthomatosis in adults. J Neurol. 2019;266(8):2043-2050. doi:10.1007/s00415-019-09377-y
7. Nobrega PR, Bernardes AM, Ribeiro RM, et al. Cerebrotendinous xanthomatosis: A practice review of pathophysiology, diagnosis, and treatment. Front Neurol. 2022;13:1049850. Published 2022 Dec 23. doi:10.3389/fneur.2022.1049850
Method Description
Describes how the test is performed and provides a method-specific reference
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)
PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information
Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.
Tuesday, Thursday
Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.
Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location
Indicates the location of the laboratory that performs the test
Fees :
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Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.
CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
CPT codes are provided by the performing laboratory.
CPT codes are provided by the performing laboratory.
82542
LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.
| Test Id | Test Order Name | Order LOINC Value |
|---|---|---|
| CTXP | Cerebrotendinous Xanthomatosis, P | 92746-7 |
| Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
|---|---|---|
| BA4379 | Interpretation (CTXP) | 59462-2 |
| BA4376 | 7a-hydroxy-4-cholesten-3-one | 92761-6 |
| BA4377 | 7a,12a-dihydroxycholest-4-en-3-one | 92758-2 |
| BA4378 | Reviewed By | 18771-6 |