How accurate are hpt? can i rely on the result? took test 8 weeks after sex. all 4 came back negative.

Reliable: If the test is done correctly and is done 7-10 days past the missed period, the results are reliable. If a correctly done test was negative at 8 week after sex, you are not pregnant.

HPT/EPT: Well some women do produce an antibody that makes their HPT turn negative even if pregnant. Those patients need a serum pregnancy test. Most urine tests are accurate and become positive at levels of 15-25miu/ml, whereas the serum test is positive at 5miu/ml. So, just a few days difference between blood and urine.