I have found the following formulae (from http://www.itl.nist.gov/div898/handbook/prc/section2/prc242.htm) to estimate the sample size required to test the binomial proportion in a single sample.
I would like to know if this is the best formula, and if $1/delta$ is really the best continuity correction, when the expected proportion is extremely low ($p_0$ < 10^-12). Is there a better, more robust formula and/or correction factor which I should use in this case?