So, for the longest time I've had this chart of hCG levels of various tests. There was one brand on there by ACON labs that was 10 mIU sensitivity, but the site doesn't seem to sell to the general public. Well, I was researching a post for my forum about HPTs and was visiting www.early-pregnancy-tests.com. And they JUST released their new Extra Sensitive Early HPTs!!!! I'm not even TTCing right now and I bought 20!!!!
If you're wondering why I'm freaking out over 10 mIU or thinking "what's an mIU?" I'll explain. With pregnancy tests (and most of the hormone tests) the lower the mIU (million International Units) the more sensitive the test. Why does this make a difference? Well, after ovulation IF an egg is fertilized it can take anywhere from 3-5 days to travel down the fallopian tubes and into the uterus where implantation occurs. This is generally believed to happen anywhere from 7-10 days past ovulation.
SO, if you've just implanted (say 7DPO) then the amount of hCG in your system will be very low (hCG isn't produced until the egg implants). Most doctors consider a blood level of < 5 mIU of hCG as NOT pregnant. Most early pregnancy tests are around 20-25 mIU (FRER (First Response Early Result) recently revised theirs to SOMETIMES 12-15 mIU). Sometimes if a woman implants early enough or produces a monster amount of hCG quickly a FRER or other early result HPT will POSSIBLY produce a faint BFP around 9-10DPO. Usually women don't see even a faint BFP until 11-12DPO (although a minority will get one earlier).
So, with an early HPT of 10 mIU you could find out earlier and with assurance that your BFP is not an evap.
One negative that I see of this and other early result tests is that if a woman is experiencing a chemical pregnancy (where a fertilized egg implants but within a week or two the pregnancy fails) then they may get the joy of achieving pregnancy but also the pain of a loss. Without early result pregnancy tests, most of these women would probably not have tested because their period might have come before they had a concern to test.
It's a risk we all take. Sometimes the dream of pregnancy has us soaring high to only to crash and burn.