“How do you detect BPD in children?”

I wish I could honestly answer this, but I’m not exactly sure what “BPD” is. Is it Bipolar Disorder? If so, then it seems way too soon to diagnose and I would get a second opinion. Otherwise, look up the DSM V diagnosis for BPD.
Hope that helps.

After working with over 500 children, I don't believe that there is such a thing as bipolar disorder in children. Most children who have had that designation are having regulation problems. My job is to help parents find ways to regulate their child with calm assertive energy - using proximity more than words. When children know you are bringing them affectionate, but firm energy, they change.