Test Catalog

Test Id : PSY

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Psychosine, Blood Spot

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Overview

Test Catalog

Useful For
Suggests clinical disorders or settings where the test may be helpful

Aids in the biochemical detection of Krabbe disease and saposin A cofactor deficiency

 

Second-tier testing or follow up testing after an abnormal newborn screening result in an infant for Krabbe disease

 

This test is not capable of identifying carriers of Krabbe disease.

 

This test is not intended for long-term monitoring of individuals being treated for Krabbe disease or for older children or adult patients at risk to develop Krabbe disease.

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

Krabbe disease (globoid cell leukodystrophy) is an autosomal recessive lysosomal storage disorder caused by an enzyme deficiency of galactocerebrosidase (GALC).

 

Although Krabbe disease is clinically variable, the most common and severe form of the disorder is early infantile onset that presents with rapid neurological regression and results in early death.

 

This test is a second-tier assay for infants who have abnormal newborn screening results with reduced GALC activity and can detect patients with infantile or late infantile Krabbe disease or saposin A cofactor deficiency.

Highlights

Psychosine elevation support a diagnosis of Krabbe disease; therefore, psychosine quantitation is a useful biomarker in determining if an individual has active disease.

 

Psychosine is also elevated in saposin A cofactor deficiency, which results in a similar clinical phenotype to Krabbe disease but patients have normal galactocerebrosidase activity.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If the patient has abnormal newborn screening result for Krabbe disease, immediate action should be taken. Refer to the appropriate American College of Medical Genetics and Genomics Newborn Screening ACT Sheet.(1,2)

 

The following are available:

-Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase

-Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase and Psychosine

 

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.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Psychosine, BS

Aliases
Lists additional common names for a test, as an aid in searching

Psychosine

Galactopsychosine

Galactosylphingosine

Krabbe disease

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If the patient has abnormal newborn screening result for Krabbe disease, immediate action should be taken. Refer to the appropriate American College of Medical Genetics and Genomics Newborn Screening ACT Sheet.(1,2)

 

The following are available:

-Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase

-Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase and Psychosine

 

Specimen Type
Describes the specimen type validated for testing

Whole blood

Ordering Guidance

This test is recommended for newborns or infants who have not had previous psychosine testing. This test is not intended to be used as a monitoring test for individuals with Krabbe disease who are treated or for children or adults at risk of developing Krabbe disease. For patients older than infancy, order PSYR / Psychosine, Whole Blood.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

Supplies: Card-Blood Spot Collection (Filter Paper) (T493)

Container/Tube:

Preferred: Card-Blood Spot Collection (Filter Paper)

Acceptable: PerkinElmer 226 filter paper, Munktell filter paper, Whatman protein Saver 903 paper, local newborn screening card, or blood collected in tubes containing EDTA (preferred) or heparin and dried on filter paper

Specimen Volume: 2 Blood spots

Collection Instructions:

1. Completely fill at least 2 circles on the filter paper card (approximately 100 microliters blood per circle).

2. Let blood dry on filter paper at ambient temperature in a horizontal position for a minimum of 3 hours.

3. Do not expose specimen to heat or direct sunlight.

4. Do not stack wet specimens.

5. Keep specimen dry.

Additional Information:

1. For collection instructions, see Blood Spot Collection Instructions

2. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777)

3. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800)

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.

1 Blood spot

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Blood spot specimen that shows serum rings or has multiple layers Reject
Insufficient specimen Reject
Nonapproved filter paper Reject

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
Whole blood Ambient (preferred) 96 days FILTER PAPER
Refrigerated 96 days FILTER PAPER
Frozen 96 days FILTER PAPER

Useful For
Suggests clinical disorders or settings where the test may be helpful

Aids in the biochemical detection of Krabbe disease and saposin A cofactor deficiency

 

Second-tier testing or follow up testing after an abnormal newborn screening result in an infant for Krabbe disease

 

This test is not capable of identifying carriers of Krabbe disease.

 

This test is not intended for long-term monitoring of individuals being treated for Krabbe disease or for older children or adult patients at risk to develop Krabbe disease.

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

Krabbe disease (globoid cell leukodystrophy) is an autosomal recessive lysosomal storage disorder caused by an enzyme deficiency of galactocerebrosidase (GALC).

 

Although Krabbe disease is clinically variable, the most common and severe form of the disorder is early infantile onset that presents with rapid neurological regression and results in early death.

 

This test is a second-tier assay for infants who have abnormal newborn screening results with reduced GALC activity and can detect patients with infantile or late infantile Krabbe disease or saposin A cofactor deficiency.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

If the patient has abnormal newborn screening result for Krabbe disease, immediate action should be taken. Refer to the appropriate American College of Medical Genetics and Genomics Newborn Screening ACT Sheet.(1,2)

 

The following are available:

-Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase

-Newborn Screen Follow-up for Krabbe Disease: Galactocerebrosidase and Psychosine

 

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Krabbe disease (globoid cell leukodystrophy) is an autosomal recessive lysosomal storage disorder caused by an enzyme deficiency of galactocerebrosidase (GALC). GALC facilitates the lysosomal degradation of psychosine (galactosylsphingosine) and 3 other substrates, galactosylceramide, lactosylceramide, and lactosylsphingosine. Krabbe disease is caused by variants in the GALC gene, and it has an estimated frequency of 1 in 100,000 births.

 

The clinical course of Krabbe disease can be variable, even within the same family. Eighty-five percent to 90% of patients present before the first year of life with central nervous system impairment, including increasing irritability, developmental delay, and sensitivity to stimuli. Rapid neurodegeneration, including white matter disease follows, with death usually occurring by 2 years of age. Late onset forms of the disease affect 10% to15% of individuals and are characterized by ataxia, vision loss, weakness, and psychomotor regression, typically presenting from age 6 months to the seventh decade of life.

 

Newborn screening for Krabbe disease has been implemented in some states. The early (presymptomatic) identification and subsequent testing of infants at risk for Krabbe disease may be helpful in reducing the morbidity and mortality associated with this disease. While treatment is mostly supportive, hematopoietic stem cell transplantation has shown some success if performed early, prior to onset of neurologic damage.

 

Psychosine is 1 of 4 substrates degraded by GALC and is a neurotoxin at elevated concentrations. It has been shown to be elevated in patients with active Krabbe disease or with saposin A cofactor deficiency and, therefore, may be a useful biomarker for the presence of disease or disease progression.

 

Reduced or absent GALC in leukocytes (GALCW / Galactocerebrosidase, Leukocytes) or dried blood spots (PLSD / Lysosomal and Peroxisomal Storage Disorders Screen, Blood Spot) along with elevated psychosine levels can indicate a diagnosis of Krabbe disease. Molecular sequencing of the GALC gene (KRABZ / Krabbe Disease, Full Gene Analysis and Large [30 kb] Deletion, Varies) allows for detection of the disease-causing variants in affected patients and carrier detection in family members.

 

Individuals with a disease phenotype similar to Krabbe disease may have saposin A cofactor deficiency. Saposin A cofactor deficiency also results in elevated psychosine levels. Testing for this condition via molecular analysis of the PSAP gene is useful in those with elevated psychosine and normal to reduced GALC activity with normal molecular genetic GALC sequencing.

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.

Normal <2 nmol/L

Interpretation
Provides information to assist in interpretation of the test results

An interpretive report will be provided.

 

An elevation of psychosine is indicative of symptomatic Krabbe disease or symptomatic saposin A cofactor deficiency.

 

When abnormal results are detected, a detailed interpretation is given, including an overview of the results and of their significance, a correlation to available clinical information, elements of differential diagnosis, recommendations for additional biochemical testing and in vitro confirmatory studies (enzyme assay, molecular analysis), and a phone number to reach one of the laboratory directors in case the referring physician has additional questions.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Normal psychosine levels may be seen in patients (from childhood to adulthood) who are not yet symptomatic or have later onset Krabbe disease or saposin A cofactor deficiency.

Supportive Data

Receiver operating characteristic curve analysis of 220 controls and 6 patients affected with Krabbe disease yielded an area under the curve of 1.0, permitting the selection of a cutoff value yielding a positive predictive value and negative predictive value of 1.0.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Newborn Screening ACT Sheet [Decreased galactocerebrosidase, elevated psychosine] Krabbe Disease (infantile form). American College of Medical Genetics and Genomics; 2021. Updated May 2022. Accessed June 10, 2024. Available at www.acmg.net/PDFLibrary/Krabbe-Infantile.pdf

2. Newborn Screening ACT Sheet [Decreased galactocerebrosidase, mildly elevated psychosine] Krabbe Disease (late-onset form). American College of Medical Genetics and Genomics; 2021. Updated May 2022. Accessed June 10, 2024. Available www.acmg.net/PDFLibrary/Krabbe-Later-Onset.pdf

3. Orsini JJ, Morrissey MA, Slavin LN, et al. Implementation of newborn screening for Krabbe disease: population study and cutoff determination. Clin Biochem. 2009;42(9):877-884. doi:10.1016/j.clinbiochem.2009.01.022

4. Svennerholm L, Vanier MT, Mansson JE. Krabbe disease: A galactosylsphingosine (psychosine) lipidosis. J Lipid Res. 1980;21(1):53-64

5. Enns GM, Steiner RD, Cowan TM. Lysosomal disorders. In: Sarafoglou K, Hoffman G, Roth KS, eds. Pediatric Endocrinology and Inborn Errors of Metabolism. McGraw-Hill Medical; 2009:744

6. Turgeon CT, Orsini JJ, Sanders KA, et al. Measurement of psychosine in dried blood spots--a possible improvement to newborn screening programs for Krabbe disease. J Inherit Metab Dis. 2015;38(5):923-929. doi:10.1007/s10545-015-9822-z

7. Wenger DA, Escolar ML, Luzi P, Rafi MA: Krabbe disease (globoid cell leukodystrophy). In: Valle D, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed August 30, 2023. Available at https://ommbid.mhmedical.com/content.aspx?sectionid=225546481&bookid=2709

8. Guenzel AJ, Turgeon CT, Nickander KK, et al. The critical role of psychosine in screening, diagnosis, and monitoring of Krabbe disease. Genet Med. 2020;22(6):1108-1118. doi:10.1038/s41436-020-0764-y

9. Thompson-Stone R, Ream MA, Gelb M, et al. Consensus recommendations for the classification and long-term follow up of infants who screen positive for Krabbe disease. Mol Genet Metab. 2021;134(1-2):53-59. doi:10.1016/j.ymgme.2021.03.016

Method Description
Describes how the test is performed and provides a method-specific reference

Internal standard is added to a dried blood spot. The extract is evaporated and reconstituted prior to injection onto a liquid chromatography tandem mass spectrometry (LC-MS/MS). Following separation of the structural isomers glucopsychosine and psychosine (PSY) by liquid chromatography, their concentrations are measured by MS/MS analysis in the multiple reaction monitoring positive mode to follow the precursor to product species transitions for PSY. The ratio of the extracted peak area of PSY to internal standard as determined by LC-MS/MS is used to calculate the concentration of PSY in the sample.(Unpublished Mayo method)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

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.

Monday through Sunday

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.

1 to 2 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

1 year

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees :
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

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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.

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
PSY Psychosine, BS 93688-0
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.
62235 Psychosine 93688-0
36342 Reviewed By 18771-6
36343 Interpretation (PSY) 59462-2

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports