How early can you take a pregnancy kit test for pregnancy?

Pregnancy test kit work by detecting the presence of hormone hCG in the urine. Within the first few weeks of implantation, the amount of hCG secreted by the woman’s body doubles every 48-72 hours. Hence, by 7 to 10 days after ovulation, a highly sensitive home pregnancy kit should be able to detect the hCG present in the urine. As a gauge, since not everyone is keeping track of her ovulation dates, one could take the test around one week after a missed period. Here is an article on the accuracy of pregnancy test kits: http://sg.theasianparent.com/how-accurate-are-pregnancy-test-kits/