Different pregnancy tests- different results- WHY?

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Different pregnancy tests- different results- WHY?
I made 2 pregnancy tests (different brands). With first one line was very vague, barely visible. The second one showed negative results. Why are results with different pregnany tests different???

mum · Joined: 16 Jan 2006 Posts: 273

test vary because different tests detect pregnancy at different level. All tests work by detecting pregnancy hormone HCG in woman's urine (meassure is MIU). Some tests detect pregnancy with as little as 20 MIU of HCG (they are very sensitive and may detect pregnancy just a few days after conception), while others demand higher level of MIU.
You must have bought 2 different pregnancy tests, i mean tests that differentiate in sensitivity: the first one must have been more sensitive than the second one.
I think it is best if you make an appointment with doc to see if you're really pregnant.