When is repeat testing needed?

[BusterBuns]

Out of curiosity, I had a HIV blood test and a Hep C blood test done through my doctor's office approximately five months after my last possible exposure.  How accurate are these tests?  I've read three months is enough for an accurate result, but is repeat testing ever needed for HIV and Hep C after a period of five months to be sure of the result, or can this be considered conclusive?  The doctor says even though nothing in the world is 100% certain, the only reason you'd get retested after so much time is to alleviate your anxiety.  Obviously the first part of that sentence made me nervous, so thought I'd pose it to the forum.

Thank you.

[Teak]

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[BusterBuns]

Apologies for the multiple posts, but I wanted to be more specific and state that I had the HIV 1/2 antibody test done if that helps at all.