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Test Catalog

Test ID: P5NT    
Pyrimidine 5' Nucleotidase, Blood

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

Evaluation of marked basophilic stippling

 

Evaluation of hemolytic anemia

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

Pyrimidine 5' nucleotidases (P5'Ns) are catabolic enzymes that regulate cellular nucleotide and nucleoside levels through the dephosphorylation of noncyclic nucleoside 5’-monophosphates. P5’N activity is much higher in reticulocytes than in aged red cells due to increased demand during erythroid maturation. Reticulocyte ribosomal RNA degradation results in pyrimidine nucleotide residues that require conversion to nucleosides to allow diffusion outside the cell. Disruption of this process results in intracellular pyrimidine nucleotide accumulation visible as coarse basophilic stippling. Several different 5'-nucleotidase (5’NT) enzymes have been identified with distinctive substrate specificity, cellular localization, and tissue distribution. Only P5’N type 1 is known to be associated with P5'N deficiency (also called uridine 5' monophosphate hydrolase deficiency), a cause of congenital nonspherocytic hemolytic anemia (OMIM 266120, autosomal recessive). The disorder manifests as mild/compensated to moderate hemolytic anemia with persistent reticulocytosis. Additional features include jaundice/neonatal hyperbilirubinemia, splenomegaly, and characteristic marked basophilic stippling on the peripheral blood smear. Coincident hemoglobin E (Hb E) may lead to a more severe hemolytic anemia. P5'N deficiency is caused by homozygous or compound heterozygous alterations in the NT5C3A gene, mapped to chromosome 7p14. Assaying for the presence of pyrimidine nucleotides serves as a surrogate marker for P5'N deficiency and is not specific for a diagnosis of hereditary P5’N deficiency. Enzyme function is magnesium ion-dependent and is inhibited by metal chelating reagents, such as EDTA. Activity is inhibited by heavy metal ions including lead, mercury, copper, nickel, and cadmium, and toxic levels can cause accumulation of intracellular pyrimidine nucleotides.

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

Interpretation Provides information to assist in interpretation of the test results

A normal result indicates the absence of pyrimidine nucleotides and indicates normal pyrimidine 5' nucleotidase (P5'N) function.

 

An abnormal result (abnormal spectral scan) indicates the presence of pyrimidine nucleotides and possible P5'N deficiency. Enzyme activity is inhibited by heavy metal ions including lead, mercury, copper, nickel, and cadmium. Toxic levels can cause accumulation of intracellular pyrimidine nucleotides. If results are abnormal clinical correlation is recommended to exclude heavy metal poisoning.

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

This assay serves as a surrogate marker for decreased pyrimidine 5' nucleotidase (P5'N) activity from any cause and is not specific for a diagnosis of hereditary P5’N deficiency.

 

Enzyme activity is inhibited by metal chelating reagents, such as EDTA.

 

Since enzyme activity is inhibited by heavy metal ions (including lead, mercury, copper, nickel, and cadmium) and toxic levels can cause accumulation of intracellular pyrimidine nucleotides, clinical correlation to exclude heavy metal poisoning is indicated forabnormal results.

 

Recent transfusion can result in false negative results.

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

1. Rees DC, Duley JA, Marinaki AM: Pyrimidine 5' nucleotidase deficiency. Br J Haematol. 2003 Feb;120(3):375-383

2. Zanella A, Bianchi P, Fermo E, Valentini G: Hereditary pyrimidine 5'-nucleotidase deficiency: from genetics to clinical manifestations. Br J Haematol. 2006 Apr;133(2):113-123

3. Fairbanks VF, Klee GG: Biochemical aspects of hematology. In: Burtis CA, Ashwood ER, eds. Tietz Textbook of Clinical Chemistry. 3rd ed. WB Saunders;  1999:1642-1647

4. Gregg XT, Prchal JT: Red blood cell enzymopathies. In: Hoffman R, Benz, Jr EJ, et al, eds. Hematology : Basic Principles and Practice, 7th ed. Elsevier; 2018:616-625

5. Warang P, Roshan C, Kedar P: Lead poisoning induced severe hemolytic anemia, basophilic stippling, mimicking erythrocyte pyrimidine 5'-nucleotidase deficiency in beta thalassemia minor. J Clin Toxicol. 2017;7(2):346. doi: 10.4172/2161-0495.1000346