I took two first response pregnancy test four days before my expected cycle. Is it safe to consider them accurate?

FIRST RESPONSE Early. Result pregnancy test is reported to detect HCG up to 6 days prior to your anticipated period. If you had 2 positive tests - that should be accurate. If you had negative test results then consider waiting until you miss your period before repeating (and use first morning void).
Week after missed pe. Pregnancy test is designed to be used about 1 week after missed period to be most accurate.