Suppress blank field with condition

I am trying to run a report with multiple diagnoses fields, but only show those that have data. But first it checks to see if a field is blank, if it is then the field will be suppressed. If not, the field prints with a name as in the following code:

If isNull({Aftercare_Plan.disch_diag_1_3_Desc})=TRUE then ""
Else
"Axis I-3: "&{Aftercare_Plan.disch_diag_1_3}&" "&{Aftercare_Plan.disch_diag_1_3_Desc}

In this example the Axis I-3 prints even though the first statement is true. Is there something else I am missing here?

Thanks for any help!