Harmony test or not?

Hi! Need suggestions on whether I should go for Harmony test. I did my OSCAR test and result was low risk 1 in 3000. However, my 20 weeks scan showed 1 common marker of Trisomy 21 (there’s an extra blood vessel in baby’s heart and that’s common in DS babies). Should I still go for harmony test? Taking note that there are no other anomalies found.