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Test Code PSY Psychosine, Blood Spot

Useful For

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.

Reporting Name

Psychosine, BS

Specimen Type

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


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)


Specimen Minimum Volume

1 Blood spot

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Ambient (preferred) 96 days FILTER PAPER
  Frozen  96 days FILTER PAPER
  Refrigerated  96 days FILTER PAPER

Reject Due To

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

Genetics Test Information

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.

Reference Values

Normal <2 nmol/L

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.

Day(s) Performed

Monday through Sunday

Report Available

1 to 2 days

Specimen Retention Time

1 year

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

82542

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PSY Psychosine, BS 93688-0

 

Result ID Test Result Name Result LOINC Value
62235 Psychosine 93688-0
36342 Reviewed By 18771-6
36343 Interpretation (PSY) 59462-2

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.

Testing Algorithm

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