Our most accurate results - 5 days sooner. Detects the early form of the pregnancy hormone. Over 99% accurate (99% accurate at detecting typical hormone levels. Note that hormone levels vary) from the day of your expected period. First Response can detect the pregnancy hormone 5 days sooner than the day of your missed period. (4 days before day of expected period.) Things to Know About Testing Early - First Response is 99% accurate at detecting the pregnancy hormone. However, some pregnant women may not have detectable amounts of the pregnancy hormone in their urine on the day they use the test. The amount of pregnancy hormone increases rapidly in early pregnancy. In clinical testing, First Response detected the hormone levels in 69% of women 4 days before their expected period, in 83 % of women 3 days before their expected period, in 93% of women 2 days before their expected period, and in 93% of women 1 day before their expected period. This kit contains 2 First Response Early Pregnancy Test sticks and instructions (in English and Spanish).