G6PD genotype-phenotype correlations

What is it about?

The diagnosis of G6PD deficiency is usually made by measuring G6PD activity in red blood cells. Genetic tests are also available, but these usually look for specific, common mutations. Because there are hundreds of mutations that can lead to a deficiency, targeted screening can fail to identify miss some individuals with rare G6PD variants. This study examined the relationship between an individual’s G6PD activity (the phenotype) and their G6PD genotype to identify a G6PD activity cutoff above which a G6PD deficiency would be considered unlikely for both males and females.

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Why is it important?

G6PD enzymatic activity tests have high diagnostic sensitivity and specificity for detecting severely deficient hemizygous males and homozygous females, but they have a lower sensitivity for detecting heterozygous females. That’s because random X chromosome inactivation leads to heterozygous females having a mixture of G6PD-deficient and -sufficient red cells. So, they can show a wide range of G6PD activities, making partial deficiencies difficult to detect.

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