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Defining Test Results

Jan 14, 2000

I work for a blood bank, and recently donated blood and have a copy of my test results . I have been deferred but have not been informed yet. Can you explain what some of the results mean. Tested "NR" for HIV-1/2 .074 (absorbance). First test for HIV1AG tested "R" .147 Second test for HIV1AG tested "NR" .082 and on third test for HIV1AG tested "R" .211. In the past, I always tested CMV negative but this time I tested CMV positive. I know this is kind of specific but I hope you can explain this to me.

Response from Dr. Holodniy

The absorbance is the amount of color generated in the test tube or microplate when an antibody/antigen complex are formed and a color dye is added to indicate that there is the presence of this complex. Almost all of these kinds of assays will have a "negative" cutoff of < 0.1, and probably much lower. That is based on what the negative controls in the assay for that particular run are showing in the test. Once the absorbance is determined to be > 0.1, it falls in the "positive" range, although most true positives will be >0.5. It is not clear yet in your case whether this is true positive or a very low false positive reading, given the negative result on the antibody screening test.


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