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Incorporating genotyping to identify patients with G6PD deficiency
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  • Sarah Morris,
  • Kristine Crews,
  • Randall Hayden,
  • Clifford Takemoto,
  • Wenjian Yang,
  • Donald Baker,
  • Ulrich Broeckel,
  • Mary Relling,
  • Cyrine Haidar
Sarah Morris
St Jude Children's Research Hospital
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Kristine Crews
St Jude Children's Research Hospital
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Randall Hayden
St Jude Children's Research Hospital
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Clifford Takemoto
St Jude Children's Research Hospital
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Wenjian Yang
St Jude Children's Research Hospital
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Donald Baker
St Jude Children's Research Hospital
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Ulrich Broeckel
Medical College of Wisconsin
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Mary Relling
St Jude Children's Research Hospital
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Cyrine Haidar
St Jude Children's Research Hospital
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Abstract

Background: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is a common X-linked enzyme disorder associated with hemolytic anemia after exposure to certain medications or foods. Activity testing is the gold standard for detecting G6PD deficiency; however, this test is affected by various hematologic parameters. Clinical G6PD genotyping is included in pharmacogenetic arrays and clinical sequencing and may be reconciled with activity results. Methods: Patients (n=1,391) enrolled on an institutional pharmacogenetic testing protocol underwent clinical G6PD genotyping for 164 G6PD variants. For the 446 patients with G6PD activity results, algorithms were designed to assign G6PD status, accounting for known interferences with the activity assay and for G6PD genotype results. We developed clinical decision support alerts to inform prescribers when high-risk medications were prescribed, warning of gene-drug interactions and recommending therapy alteration. Results: Of 1,391 patients with genotype, 1,334 (95.9%) patients were predicted to have normal G6PD activity, 30 (2.1%) were predicted to have variable G6PD activity, and 27 (2%) were predicted to have deficient G6PD activity. Of the 417 patients with a normal genotype and an activity result, 415 (99.5%) had a concordant normal G6PD phenotype. Of the 21 patients with a deficient genotype and an activity result, 18 (85.7%) had a concordant deficient activity result. Genotyping reassigned phenotype in 5 patients with discordant genotype and activity results: 3 switched from normal to deficient, and 2 switched from deficient to normal. Conclusion: G6PD activity and genotyping are two independent testing methods which can be used in conjunction to assign a more informed G6PD phenotype.