How accurate are home pregnancy tests on the first day of a missed period?
An October 2001 JAMA article (JAMA. 2001;286:1759-1761) said the highest possible screening sensitivity for an hCG-based pregnancy test conducted on the first day of a missed period is 90 percent, as 10 percent of women may not have implanted yet. The authors estimate that the highest possible screening sensitivity of a home pregnancy test by one week after the first day of the missed period is 97 percent.
The accuracy of a home pregnancy test always depends on when you take it and how well you follow the instructions and interpret the results. In ideal conditions, home pregnancy tests are an estimated 90 percent accurate when taken on the same day you miss your period. If you take a home pregnancy test one week after the first day of your missed period, however, accuracy increases to an estimated 97 percent.
