Over 99% accurate (Over 99% accurate at detecting typical pregnancy hormone levels. Note that hormone levels vary) from the day of your expected period. Results 5 days before missed period. Testing before missed period? The EPT Certainty 1-step pregnancy test can be used up to 4 days before your expected period, which is 5 days sooner than waiting until you miss your period to test. However, the distributor of EPT Certainty 1-step recommends waiting until the day of your expected period for more accurate results. If you want to test earlier, keep in mind that levels of the pregnancy hormone very greatly, which makes testing earlier less reliable. If you test early and get a negative result, the distributor of e.p.t. Certainty 1-Step recommends retesting on the day of your expected period. Clinical Results with Early Pregnancy Samples: 1 Day Before Expected Period: 95% of pregnant women got a pregnant result with EPT. 2 Days Before Expected Period: 90% of pregnant women got a pregnant result with EPT. 3 Days Before Expected Period: 82% of pregnant women got a pregnant result with EPT. 4 Days Before Expected Period: 51% of pregnant women got a pregnant result with EPT. Easy to Read: Unmistakable pregnant or not pregnant read-out. Made in UK.