I was also going to mention doing the test on the full moon. I once attended a seminar by a doc who does a lot of parasite testing. Someone told him about the full-moon thing, so he went back over the previous 5 years and compared the percentage of positive stool samples by patients who took the sample on or within three days of a full moon, with patients who took their stool sample at other times.
I forgot the details, but I think 2 and half times as many patients who had taken their sample around the full moon tested positive.