Normal ALT Levels = No HCV?

Hi all-
I'm waiting to get my viral load numbers this week.  Blood test last week showed ALT of 47 and AST of 36.

The last blood test results I have are from 4 years ago and both my ALT and AST were totally in the normal range.  Does that mean it is likely I contracted the HCV in the past 4 years, or could I have had it before that but still have had normal ALT levels?

I know I'll probably never figure out where I got it, but I'd love to be able to narrow down the time frame a little.

Can't seem to find the answer on the Internet, hoping someone here might have an opinion.

Take care,
Rebecca