Well if i was the guy and i knew that my gf slept around with a lot of guys, then i had request her to do a blood test for STDs. I had be more interested in her blood result than the number of guys she slept with. If the result was clear, then only i would marry her.
If i was the girl, i had use mathematics to answer the question like >1  <5 and i would gladly do the blood test. I would also not marry this guy anymore as respect would have been lost.