I really have problems with some semantics, grammar and parsing here.
First: 行われた. Something didn't "do" or "perform". In the overall sentence, I dont know how to meaningfully integrate this. Second: か国で I guess the か could be some kind of suffix for counting countries. で is probably the particle で here? It would somehow make sense at least in the way I understand the sentence. Third: 国際調査 "international investigation". I don't know what interpretation from a syntactic perspective would be correct. "The international investigation which didn't do/perform in 80 countries." or "The international investigation about: It doesn't do in 80 countries."
My attempt at a full translation would be: "The results of an international investigation, which didn't do in 80 countries, were published."
EDIT: 行われた is not negative form, as pointed out by lelecteur. Besides I also noticed that its passive, or better said, that I forgot to translate passive...^^ Therefore, the attempt at translation should be: "The results of an international investigation, which was performed in 80 countries, were published.