Tripeptidyl Peptidase 1 (TPP1) and Palmitoyl-Protein Thioesterase 1 (PPT1), Leukocytes
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Evaluation of patients with clinical presentations suggestive of neuronal ceroid lipofuscinoses (NCL)
An aid in the differential diagnosis of infantile and late infantile NCL
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
TPP1 and PPT1, WBC
Palmitoyl-Protein Thioesterase 1 (PPT1)
TPP1 (Tripeptidyl Peptidase 1)
NCL (Neuronal Ceroid Lipofuscinosis)
Palmitoyl-Protein Thioesterase 1 (PPT1)
TPP1 (Tripeptidyl Peptidase 1)
NCL (Neuronal Ceroid Lipofuscinosis)
Specimen Type Describes the specimen type needed for testing
Whole Blood ACD
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Specimen must arrive refrigerate within 72 hours of draw to be stabilized. Draw specimen Monday through Thursday only and not the day before a holiday. Specimen should be drawn and packaged as close to shipping time as possible.
Preferred: Yellow top (ACD solution B)
Acceptable: Yellow top (ACD solution A)
Specimen Volume: 7 mL
Collection Instructions: Do not transfer blood to other containers.
1. 1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.
2. 2. If not ordering electronically, submit a Biochemical Genetics Request Form (Supply T439) with the specimen.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Mild OK; Gross reject
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
|Whole Blood ACD||Refrigerated||72 hours|
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
The neuronal ceroid lipofuscinoses (NCL) comprise a group of recessively inherited neurodegenerative disorders involved in lysosomal protein catabolism. Clinically they are characterized by vision loss, seizures, mental regression, behavioral changes, movement disorders, and the accumulation of storage material with a characteristic appearance by electron microscopy. Currently, at least 10 genetically distinct NCLs (CLN1-CLN10) are known. The age of onset and rate of deterioration varies according to type of NCL. Tissue damage is selective for the nervous system and many patients die in the first decade of life due to central nervous system degeneration. There is an overall incidence in the United States estimated at 1 in 12,500.
Children affected by infantile NCL (CLN1) typically have normal growth and development until about 6 to 12 months of age. Slowed head growth occurs at around 9 months followed by psychomotor degeneration, seizures, and progressive macular degeneration leading to blindness by the age of 2. CLN1 is caused by a deficiency of the lysosomal enzyme palmitoyl-protein thioesterase 1 (PPT1), which cleaves long-chain fatty acids (usually palmitate) from cysteine residues. Electron microscopy shows granular osmophilic deposits (GRODs) in most cell types. PPT1 is thought to play an active role in various cell processes including apoptosis, endocytosis, and lipid metabolism. Infantile NCL has an incidence of 1 in 20,000 in Finland and is rare elsewhere.
The late infantile form of NCL (CLN2) is caused by deficiency of the lysosomal enzyme tripeptidyl peptidase 1 (TPP1), which cleaves tripeptides from the N-terminus of polypeptides. Tissue damage results from the defective degradation and consequent accumulation of storage material with a curvilinear profile by electron microscopy. There is widespread loss of neuronal tissue especially in the cerebellum and hippocampal region. Disease onset occurs at 2 to 4 years of age with seizures, ataxia, myoclonus, psychomotor retardation, vision loss and speech impairment.
Diagnostic strategy depends on the age of onset of symptoms. In children presenting between the ages 0 to 4 years, enzyme assay of PPT1 and TPP1 is an appropriate first step. In addition, molecular genetic testing of CLN1 or CLN2 may allow for identification of the disease causing mutations.
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.
TPP1: 85-326 nmol/hour/mg protein
PPT1: 20-93 nmol/hour/mg protein
Tripeptidyl peptidase 1 (TPP1) and palmitoyl-protein thioesterase 1 (PPT1) enzyme activity below 5 nmol/hour/mg of protein are highly suggestive of late-infantile and infantile neuronal ceroid lipofuscinoses, respectively.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This assay does not detect carrier status of neuronal ceroid lipofuscinoses.
Some variants with an age of onset occurring in older individuals have been noted.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Haltia M: The neuronal ceroid-lipofuscinoses: from past to present. Biochim Biophys Acta 2006;1762:850-856
2. Kavianen R: Juvenile-onset neuronal ceroid lipofuscinosis with infantile CLN1 mutation and palmitoyl-protein thioesterase deficiency. Eur J Neur 2007;14:369-372
3. Enns GM, Steiner RD, Cowan TM: Lysosomal disorders. In Pediatric Endocrinology and Inborn Errors of Metabolism. Edited by K Sarafoglou, GF Hoffmann, KS Roth, New York, McGraw-Hill Medical Division, 2009, pp 749-750
Method Description Describes how the test is performed and provides a method-specific reference
The synthetic substrate for palmitoyl-protein thioesterase 1 (PPT1) is 4-methylumbelliferyl-6-thiopalmitoyl-beta-glucoside. The leukocytes are homogenized. Approximately 10 mcg of protein is combined with substrate and incubated at 37 degrees C for 1 hour. The reaction is stopped with a glycine buffer. The fluorescence of the 4-methylumbelliferone product is read using a fluorescence plate reader and activity is calculated based on amount of product formed during the 1 hour incubation period.(Van Diggelen OP, Keulemans JLM, Winchester B, et al: A rapid fluorogenic palmitoyl-protein thioesterase assay: Pre and post natal diagnosis of INCL. Mol Genet Metab 1999;66:240-244)
The synthetic substrate for tripeptidyl peptidase 1 (TPP1) is Ala-Ala-Phe-7-amido-4-methylcoumarin. The leukocytes are homogenized. Approximately 5 mcg of protein is combined with substrate and incubated at 37 degrees C for 1 hour. The reaction is stopped with a glycine buffer. The fluorescence of the 7-amino-4-methylcoumarin product is read using a fluorescence plate reader and activity is calculated based on amount of product formed during the 1 hour incubation period.(Sohar I, Lin L, Lobel P: Enzyme-based diagnosis of classical late infantile neuronal ceroid lipofuscinosis: comparison of tripeptidyl peptidase I and pepstatin-insensitive protease assays. Clin Chem 2000;46:1005-1008)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
WBC homogenate stored for 1 month
Performing Laboratory Location The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. 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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
|Result ID||Reporting Name||LOINC Code|
|50692||Reason for Referral||42349-1|