To the best of my knowledge, this is what I gather the table's values mean:
"antibodies present" and "positive" give you the percent of people who had the antibodies and the tests showed they did (hence, positive).
"antibodies present" and "negative" give you the percent of people who did have the antibodies, yet the tests read otherwise (misdiagnosed, negative when it should be positive).
"antibodies not present" and "positive" also show a percentage of people who were misdiagnosed. these people did not have the antibodies yet they tested positive for them.
"antibodies not present" and "negative" show the percent of people who did not have the antibodies and who were tested to prove just that.
