Rapid antigen test.
Possible complications of untreated or partially treated strep throat infection are:
https://www.timetoast.com/timelines/strep-throat-history
http://www.mayoclinic.org/diseases-conditions/strep-throat/symptoms-causes/dxc-20165964
http://www.webmd.com/oral-health/tc/strep-throat-topic-overview#1
http://www.medicinenet.com/strep_throat_complications/views.htm
https://www.timetoast.com/timelines/strep-throat-history