85379-6

LOINC 2.82

Purine/Pyrimidine [Ratio] in Red Blood Cells by Spectrophotometry

Purine/Pyrimidine RBC Spect-Rto

Definition

  • The purine to pyrimidine ratio is a marker of pyrimidine-5-nucleotidase (P5N) which is an enzyme in the cytoplasm of human red blood cells. The function of P5N is unknown but a deficiency of the enzyme causes congenital haemolytic anemia. Individuals who are heterozygous for the recessive P5N gene demonstrate no clinical or hematological abnormalities while those homozygous for the recessive P5N gene have a corresponding 5-30% reduction in normal enzyme activity. P5N deficiency leads to chronic non-spherocytic haemolytic anaemia associated with mild to moderate hemolysis, increased basophilic stippling in 5% of the red blood cells and an elevation of red cell glutathione and pyrimidine nucleotides. The diagnosis of P5N deficiency is based on the change in the level of cytidine and uridine in red blood cells which is normally very low but increases to over 50% in P5N deficient patients. Measurement of P5N is by light absorption at different wavelengths. In acidic solution pyrimidine nucleotides absorb the maximum amount of light at 280 nanometers (nm). Purine nucleotides absorb the maximum amount of light at 260 nm. The ratio of light absorbed at 260 nm to that at 280 nm in a pool of red blood cells indicates the relative amount of purines to pyrimidines. The ratio is lower than normal when pyrimidine levels are increased.[PMID: 23992312][ Dacie and Lewis Practical Haematology, 11th edition, Barbara J. Bain, Imelda Bates, Mike A. Laffan, S. Mitchell Lewis, p259]

Component

  • Purine/pyrimidine

Specimen / system

  • RBC

Class

  • CHEM

Property

  • Ratio

Scale

  • Qn

Method

  • Spectrophotometry

Related names

  • Chemistry; Erythrocytes; Point in time; QNT; Quan; Quant; Quantitative; Random; Ratios; Red blood cells; Red blood corpusles; Rto

Index terms

  • Chemistry
  • Erythrocytes
  • Point in time
  • QNT
  • Quan
  • Quant
  • Quantitative
  • Random
  • Ratios
  • Red blood cells
  • Red blood corpusles
  • Rto