Diagnostic study of choice for G6PD deficiency include quantitative laboratory assay, Beutler fluorescent spot test and DNA testing for mutated genes.

Testing for G6PD deficiency may be done in the following settings:^[1]

• Neonatal jaundice
• Unexplained hemolytic anemia
• High risk patients before administration oxidant medications such as nitrofurantoin
• High risk patients before administering rasburicase for tumor lysis syndrome
• Asymptomatic family members

Quantitative laboratory assay for G6PD enzyme activity

Beutler fluorescent spot test is the gold standard test for the diagnosis of G6PD deficiency. This test detects NADPH produced by G6PD under ultraviolet light.^[2]

DNA testing for mutated genes

• G6PD enzyme activity less than 5 units per gram of hemoglobin in quantitative laboratory assay is considered G6PD deficiency.

• The following result of Beutler fluorescent spot testis is confirmatory of G6PD deficiency:
  • No fluorescence under ultraviolet light. False negative result in active hemolysis, so this test is done 2-3 weeks after hemolysis.