I have tried using the following:

'401.PatientAgeGroup' =

CASE

WHEN [400.PatientAge] > 18 AND pp.PatientSex = 'M' THEN 'E'

WHEN [400.PatientAge] > 18 AND pp.PatientSex = 'F' THEN 'D'

WHEN [400.PatientAge] BETWEEN 7...