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Test ID: P5NT Pyrimidine 5' Nucleotidase, Blood

Reporting Name

Pyrimidine 5' Nucleotidase, B

Useful For

Evaluation of marked basophilic stippling


Evaluation of hemolytic anemia

Specimen Type

Whole Blood ACD-B

Specimen Required


Preferred: Yellow top (ACD solution B)

Acceptable: Lavender top (EDTA)

Specimen Volume: 5 mL

Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood ACD-B Refrigerated 20 days

Reference Values


Day(s) Performed

Monday through Friday

Test Classification

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 US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
P5NT Pyrimidine 5' Nucleotidase, B 2902-5


Result ID Test Result Name Result LOINC Value
2734 Pyrimidine 5' Nucleotidase, B 2902-5

Clinical Information

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.


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.

Clinical Reference

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

Report Available

10 days

Method Name

Kinetic Spectrophotometry


If not ordering electronically, complete, print, and send a Benign Hematology Test Request Form (T755) with the specimen.

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