What tests should be performed in the diagnosis of glucose-6-phosphate dehydrogenase (G6PD) deficiency?

Updated: Feb 19, 2019
  • Author: Srikanth Nagalla, MBBS, MS, FACP; Chief Editor: Emmanuel C Besa, MD  more...
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Answer

Testing should include the Beutler test and a quantitative assay of GPD activity. [13, 14, 21, 29] The Beutler test is a semi-quantitative rapid fluorescent spot test that detects the generation of nicotinamide adenine dinucleotide phosphate (NADPH) from nicotinamide adenine dinucleotide phosphate (NADP); the test is positive if the blood spot fails to fluoresce under ultraviolet light. The Beutler test is not reliable in females. [4] }

A spectrophotometric analysis of G6PD activity in a leukocyte-depleted sample is the standard quantitative test. Testing for enzyme activity should be performed when patients are in remission, as results may be falsely negative during acute hemolysis. The reason is that older erythrocytes have been destroyed, because their diminished G6PD levels leaves them vulnerable to hemolysis while there is a compensatory increase of immature erythrocytes and reticulocytes that have increased G6PD levels.

However, spectrophotometric analysis may fail to detect G6PD deficiency in hemizygous patients. Also, spectrophotometric quantitation may fail to detect deficiency in heterozygous females due to residual activity in G6PD-sufficient cells. The identification of G6PD-deficient as well as G6PD-sufficient cells by a cytochemical method or cytofluorometry is more sensitive in the testing for G6PD deficiency in females. Chromate inhibition is a test that is more sensitive than spectrophotometric quantitation for heterozygous G6PD deficiency in females. [30, 31]

 G6PD activity is higher in premature infants than in term infants. This should be considered when testing for G6PD deficiency in infants. [32]


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