I don't know about that. I got a positive urine pregnancy test 8 days after ovulation with a Wondfo. I am positive on my dates and my dates were later confirmed with an early ultrasound at 6 wks 3 days. By the next day (9dpo) all tests including the digital, which are supposed to be less sensitive, we're positive. If the article is right and it takes four or five days post implantation to get a positive urine test then implantation would have occurred 4 days after ovulation and I find that highly unlikely.