the first time i got pregnant, we used a pregnancy test kit because we want to know first before anybody else in the laboratory does :)
its 99% accurate...
so, if you get a positive result and still want to check it thru laboratory test, then go for it, anyways, you will surely still have to visit the doctor and then will advice you to take the pregnancy blood test which is the most accurate of course.
if you got a negative result and still ended up thinking because you've been experiencing various pregnancy symptoms, then go get the pregnancy blood test. :-)