Of course at $1/15m/test, a battery of tests is practically built in to the price. If the instructions are to "take three cards and put a drop of blood on each," and that it isn't a positive result unless all three agree, you've solved that problem.
Highly unlikely that three runs of the same test are fully independant, i.e. they might match all on the same antibody which is similar to an HIV one but not due to a HIV. You likely only prevent operation goof-ups like "oops, spilled a bit of blood from the needle of my bro here ..." (or something less fancy and more likely).
Which is why in practice you run a different test to confirm results.
