Hi, My Wife Had Her Last Period On 9/23 And

Hi, my wife had her last period on 9/23 and she has done a course of Duphaston which ended on 10/23. She hasn't got a period as yet and we took a home pregnancy test which came positive. I wanted to know if Duphaston can lead to a false home pregnancy test?

What blood work do we need to do to be sure?