Blood Drug Testing - How accurate were blood typing tests in the 60's and earlier?

How accurate were blood typing tests in the 60's and earlier?

Were there ever any problems with accuracy regarding these tests?

Let us make sure we are talking the same thing so we don't waste time. Correctly, blood typing means like A+, B-, O+ and so forth. This was much more primitive than today's DNA tests. Yes, long before 1960, this type of blood typing was considered reliable and repeatable. Since they first used blood transfusions, they knew it was necessary to use the correct blood type to keep from killing the patients with donated blood. In MASH TV programs, it was a common and accurate theme to discuss running low on certain blood types in a show. Was it possible for a given lab tech at a given moment to make some sort of mistake? Always. But, this would not have happened much since the consequences were so bad. As an aside, there are certain blood types in the mother and father which cannot possibly produce certain blood types in the child. Before DNA tests, that was the only way a man could prove a child was not his.