LOINC display name : Purine/Pyrimidine Spectrophotometry (RBC) [Ratio];
LOINC long common name : Purine/Pyrimidine [Ratio] in Red Blood Cells by Spectrophotometry;
LOINC short name : Purine/Pyrimidine RBC Spect-Rto;
LOINC description : 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];
Has component