Brief Answer:
Unlikely to be positive, get 4th generation testing to be 100% sure

Detailed Answer:
Hello XXXX,
I have gone through your question and understand your concerns.

The risk of HIV transmission through oral sex is much less than that from anal or vaginal sex—but it is not zero.
The testing of HIV depends upon period of exposure , type of testing done and anticipated window period.
Best test in early days is 4th generation testing as it measures both antibodies and antigens. The window period is 11 days to 1 month.
Third generation test are also good but window period is long 3 months when antibodies formation occurs at detectable levels.
To be sure either you go for 4th generation testing or repeat 3rd generation testing after around 2-4 weeks.
Chances are less to be positive as exposure related risk is less and previous test (3rd generation) is also negative at 91 days.
Hope you found the answer helpful.
Regards
Dr Deepti Verma

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Brief Answer:
Cut off is not absolute

Detailed Answer:
Hello XXXX,
The 3rd generation testing is antibodies based and antibody formation varies from individual to individual and also with amount of exposure.
The antibodies formation is more and early if antigenic exposure is more.
The 3 months cut off is not absolute and should be interpreted with some margin. Though you have very less chances of any significant risk it will be more than reassuring if you repeat the test.
Guidelines are guide to maximum people and takes cut off of 2 standard deviation but 100% purity and coverage is not provided.
Hope you found the answer helpful.
Regards
Dr XXXXXXX XXXXXXX
Neurologist

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