An update, I've tried porting this equation:
=IF(AND((SpecimenDate-AdmissionDate)<=2,SpecimenDate>=AdmissionDate),"PRE-48h",IF((AND((SpecimenDate-AdmissionDate)>2,SpecimenDate>=AdmissionDate,AdmissionDate<>"")),"ACUTE","COMMUNITY"))
using the Expression builder to get...