If the DNA matched that's means that sarada could have her dna because karin implanted her cells in sarada when she was born. Suigetsu just make the test with karin's material not sasuke's material. But sarada has sakura and sasuke DNA too of course. But it strange that karin still has her umbilical cord. Why do you think karin didn't want suigetsu to touch her stuff? And he said he was not sure that the cord was from karin