Abnormal quad screen

Jen
I'm wondering if anyone has been in similar situation that I am in. I got a call from my doctor yesterday saying my quad screen came back "at risk" for trisomy 18. The test showed 1:82 chance of trisomy. She also told me that the test is only about 50% accurate. 
I am now waiting to get the Harmony or maternity-21 test done next week. 
Has anyone been through this before? I had my anatomy scan last week and everything looked normal so that makes things even more confusing. 
I'm just so confused and worried about my baby boy!