I have read that HSV1 and HSV2 IgG tests should be administered around 12 weeks after suspected exposure for best accuracy.  However, my doctor said that since I had a suspicious penile rash and swollen lymph nodes, my negative IgG result (blood drawn 10 days after rash appeared) was very accurate after 10 days.

Your doctor is totally mistaken.  At 3 weeks out from a concerning encounter, only half the people who eventually were positive, were positive.  So 10 days is definitely not conclusive.  If you already had established infection, something you've had for a while, then sure, 10 days is fine, but not if you are worried about a new infection.  Was the rash swab tested for herpes?  That is the standard of care - if there is something to swab, swab it.  If there is no physical symptom, you can try to determine infection by a blood antibody test.  Or you can both to try to determine if the infection is new.

Terri
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My reason for seeing the doctor was because the penile rash appeared.  I dont have any suspicious encounters, but my non-symptomatic partner has also taken the IgG test (no results yet).   My doctor's visual exam was inconclusive - the 4 blisters looked consistent with HSV, but they were spread around with 5mm gaps instead of clustered, so he was not convinced it was positive.  No swab test was done, and there are no new blisters as of now.  I have never had a rash/blemish on my penis like this before.  He did prescribe a 2 day course of valtrex.  I am now 16 days after the rash first appeared.

Too bad you didn't get a swab test.  That would have clarified the type and the location of your infection, if the antibody test comes back positive.  But what's done is done. 
Herpes blisters don't have to be in groups - they can be separate. 
Yes, I would recommend another test at 12 weeks - you could also test at 6 weeks and see if anything is different. 
And your partner's IgG test will be very useful in determining if you are different or the same in terms of your herpes status.
Can you describe the rash and the stages it went through a bit more for me please?\

Terri
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A single bump that blistered and popped and scabbed over, followed by 3 more that did the same 5 days later.    What is the test accuracy after 6  weeks?   Would you recommend I try for a 2nd opinion to obtain a preventative antiviral prescription?

If you take antivirals now, I can interfere with your antibody test results - I wouldn't suggest it yet.
They do sound worrisome to me - if you get any more - please get them swab tested right away.
an antibody test done at 6 weeks should be 70% accurate - that is, if you repeat the test at 12 weeks, there is a 70% chance the result will be the same as it was at 6 weeks.

Terri
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