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Question about test reliability

Sep 10, 2004

Dr Bob, I've seen your consistant answers about the reliability of the Elissa tests, but a question/answer from another doc didn't seem as certain.

"Please help me understand! I had a EIA test done it came back negative. Then had a PCR test done which came back showing HIV-1 rna quant by 750,000 and absolute cd4 at 222. Then the doctor had a western blot done it's results: positive gp 160/120 present p65 present p55 present p51 present gp41 present p40 present p31 absent p24 present p18 present it has been stated here at this web site that western blot should not be used unless you have a pos EIA.So Iam I HIV + ? Should I have a EIA test done again & what if it comes back negative?"

The answer was that from the data, it appears as if the person IS indeed, HIV positive.

I'm having severe problems, but have tested negative myself. What's your take on the above letter and answer? Thanks for your response.


Response from Dr. Frascino


If those test results are accurate, I would agree the data would indicate the person is HIV positive. That would mean the EIA was a "false-negative."

False-negative results are usually due to testing in the "window period." The rate of false-negatives ranges form 0.3% in a high-prevalence population to less than 0.001% in low-prevalence populations. Causes of false-negative results include:

1. window period

2. agammaglobulinemia

3. late-stage seroreversion

4. atypical host response

5. type N or O strains or HIV-2

6. technical or clerical error

Without additional details, I cannot speculate as to which of these causes may have accounted for the original questioner's false-negative EIA.

Don, despite the very unusual situation described above, please realize that standard serological assays (EIA and WB) demonstrate remarkable sensitivity and specificity. Positive tests should be confirmed with repeat tests or with corroborating clinical and laboratory data. However, if you have tested repeatedly negative, you should look elsewhere for the cause of your "severe problems."

Hope that helps clarify things for you.

Dr. Bob

Nucleic Acid Testing -vs- P 24 antigen -vs- Antibody test's
This one is NOT in the archives YET!

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