||This is where hishtadlut comes in. We need to do our effort and then we can leave the rest up to Hashem. My father loves to say, Hashem has been running the world very well till now, we don't need to help Him. But, we have a chiyuv to do our hishtadlut. That would include, according to most, avoiding a marriage that has a higher chance of disease.
This issue is a tough one, because there are those who will not go out without the test being done. Why make it harder than it is already, to find a shidduch. A wedding costs Thousands. Why save $200.