Dear Doctor: Is this HIV test accurate?

DEAR DR. ROACH:

I had HIV exposure with someone who is confirmed as HIV positive (he admitted it when I confronted him). For a different reason, I was administered a three-day dexamethasone injection of high dosages. It was on the 11th, 12th and 13th day after exposure. I continue to experience symptoms: diarrhea, rashes, weakness, two swollen lymph nodes in my neck and rapid weight loss. My fourth-generation HIV test, which I took 70 days post-exposure, returned with a nonreactive result. My question is, can the dexamethasone injection affect the lab test and give a false negative result? — A.L.

ANSWER:

Few test results cause as much stress as an HIV test, but after 70 days, the results of a fourth-generation test (which looks for both HIV antibodies and a viral antigen called p24) are extremely accurate. Seventy days after exposure, the minimum sensitivity is 99.8%, and most studies show 100%. There is never a guarantee, but it is much more likely that your symptoms are caused by stress or something entirely unrelated. The dexamethasone injection you took has no effect on the HIV results now.

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Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to [email protected] or send mail to 628 Virginia Dr., Orlando, FL 32803.

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