I'm not a medical professional nor an expert on laboratory testing, but my layman's understanding of PSA testing machines is that they have to be routinely calibrated and in studies testing their accuracy there's an error range. I totally understand your concern, but my first psa test done 3 months after surgery was .04. I was a bit worried until I spoke with my brothr who, coincidentally, happened to get a psa test around the same time at the same lab. His test had also come back as .04 even though his psa has been undetectable for 2 decades. He just matter of factly told me that mine was just the machine and my psa was probably undetectable. Sure enough, my next psa test they did it on a different type of machine and it was < .1. Since then the lab did my last 2 tests on the same type of machine as the first time and it's been < .04. I think the trend is more reliable compared to one reading with such a slight difference. Just my 2 cents. Best wishes.