26th February 2025

A 35-year-old female with known SLE is seen in clinic.

A 35-year-old female with known SLE is seen in clinic. She has had well-controlled disease for some time and would like to start a family. She would like to discuss her medication options with you. She currently takes hydroxychloroquine 200 mg once daily and mycophenolate mofetil 500 mg twice daily. 

You agree that she will stop mycophenolate mofetil and replace this with azathioprine, as she can take this safely throughout pregnancy. 

Which blood test is required prior to commencing azathioprine?

Select the SINGLE most appropriate option from the list below. Select ONE option only.