If a girl takes a pregnancy test 11 days after conception will it be accurate? this was a first response rapid response test and it was taken after a missed period.

If : If the test was taken after a missed period then yes it should be accurate. It can detect pregnancy about 6 days before a missed period. To clarify what you stated in your post, 11 days after conception would be before her period is due. For example if a girl ovulates on day 14 of her cycle, her period is due about 14 days later unless conception has occurred.

Pregnancy test: If you had sex since your last period and missed your period by 4-5 days, do a home pregnancy test. If the result is negative repeat the test 4-5 days later unless you get a period by then. Use first morning urine and follow the instructions for the test carefully. If you do not wish to be pregnant, use contraception all the time, every time. You may consider implanted contraceptive, or IUD.