or does it take the same amount of time.

Same amount of time.

Edit: Though the time difference might be at the doctor's side, since they get the test results first, and if it's positive, then they might have to arrange for counselling. Or the lab might have a backup of tests to run, which would mean they're running behind. The same, I expect. Either a reaction will happen or it won't. Same amount of time... they do the test and wait for the results. I'd say the same, since you practice the procedure on the sample, to get an outcome, how long it takes for conditions to be proper for the annalist to come to a conclusion, shouldn't depend on the conclusion No difference. It will either come up positive or negative in the same amount of time.