BabyCenter reports that a faint line on an EPT test is considered to be a positive result as long as the test is read within the specified time frame. Faint positives are generally due to low levels of human chorionic gonadotropin.
HCG is the hormone detected by home pregnancy tests. When a woman is newly pregnant, her HCG levels are still fairly low. Low HCG levels will yield a lighter line on a pregnancy test than higher HCG levels. For pregnancy tests that are not very sensitive, faint lines are common early in the pregnancy because the test requires a higher HCG level in order to be positive.
A pregnant woman's HCG levels double approximately every 48 hours. If a woman receives a faint positive, she should retest again in 2 days. This gives her HCG a chance to significantly increase, which should provide a darker line on her pregnancy test.
It is vital that the results on an EPT pregnancy test be read within 10 minutes as directed by the manufacturer's instructions. A faint line that appears after 10 minutes is not considered to be a valid positive. Pregnancy tests can yield something known as evaporation lines. Evaporation lines are colorless lines that appear outside of the testing window once the test strip has dried.
If a woman's pregnancy test is still faint after retesting a couple days later, she should contact her doctor. The doctor can perform blood work to determine if her HCG levels are increasing at an appropriate rate.