When is the earliest a pregnancy test (BETA hcg) will be accurate?

A qualitative urine or blood hCG test is ordered as early as 10 days after a missed menstrual period if a woman wishes to confirm whether or not she is pregnant (some methods can detect hCG even earlier, at one week after conception). In certain patients, several quantitative blood hCG tests over several days may be ordered to rule out an ectopic pregnancy or to monitor a woman after a miscarriage. A doctor will also order a quantitative hCG test when she suspects trophoblastic disease or the presence of germ cell tumors.

this info is found in this website: http://www.labtestsonline.org/understanding/analytes/hcg/test.html

i guess it will tell the correct result 11 days after the conception...

im not really sure though, but im able to have positive result a day after my expected date of menstruation...