Do you check the Duffy-null phenotype before starting azathioprine and in which patients?

Do you check the Duffy-null phenotype before starting azathioprine?

• No, I do not check duffy-null phenotype
• Yes, I check duffy-null phenotype prior to starting azathioprine
• Yes, I check duffy-null phenotype in patients at increased risk (baseline leukopenia, African ancestry)
• Other