AFP confusion!

I posted awhile back about my AFP level (20.9 n/g a few months ago & 18.4 last month).  In a recent post, I learned that anyone with an AFP over 7 should be tracked for cancer.  I started freaking out (even though I had a CT scan showing no tumors, three sets of normal liver panel scores, a very low viral load, and the distinct possibilty that I've been infected 3 months)...now I see that AFP can be measured in both I.U.'s & n/g (nanograms).  My lab uses n/g, though I.U. is probably more common.  Here is the breakdown of "acceptable" AFP levels according to Kaiser:

Men and nonpregnant women: 0

[WaveRider]

Mr Potter - "I had a CT scan showing no tumors". Normal CT Scans will NOT uncover a liver tumor only a scan performed with Contrast fluid. So I'm hoping you had the last performed.