The Body Covers: The 47th Interscience Conference on Antimicrobial Agents and Chemotherapy
ICAAC 2007 Study Summaries: An Interview With Thomas Nugent, Ph.D.
September 19, 2007
My name is Tom Nugent. I'm with Gen-Probe Inc. in San Diego, California.
Can you walk me through your study?
Sure. What we have here on the poster describes the APTIMA HIV-1 R in a qualitative assay, which is the first nucleic acid test, or NAT test, that has been approved by the FDA [U.S. Food and Drug Administration] for diagnosis of acute HIV. So, what we wanted to do here with our collaborators at UCSD (University of California, San Diego) was to determine if we can use this test in a quantitative, or semi-quantitative, kind of fashion. Because our test here, as it's described, is a qualitative test where you're actually looking at whether there is HIV present in the plasma: yes or no.
What we did was actually look at our cut-off for before the sample is either HIV infected or not and see if we could synthetically raise the cut-off to actually determine whether clinically relevant samples, or those samples that are greater than 50 copies/mL that need to go on to be quantitated, can be separated from the samples that are less than 50 copies/mL. Those samples basically are not clinically relevant. They can actually not be of any value to the position.
What we found was actually that if we raised this sample cut-off up to 15, as shown in Table 2 in the masked study, we actually kept all of the samples that were 51 to 400 copies/mL, except for one sample that was 72 copies/mL; that would kind of be a sample that would be clinically relevant. It's just right above the cut-off. But, importantly, the samples that are 401 copies, and all the way up to greater than 3,000 -- I believe there were some that were 15,000 to 20,000 copies/mL -- all those samples were actually kept or caught by our test.
In conclusion, the results suggest that we could increase the SCO, or the sample cut-off, and it could be useful in determining whether samples from patients under therapy may be need to be sent for quantitative HIV testing. In the masked study, were we to blind this study with UCSD patient samples, it would have reduced the number of samples for quantitative testing from 115 down to 57, or about 49 to 50%, and it would have been a good cost savings for the clinics. So that's pretty much the quick walk through.
What was your study population like?
The study population were HIV-positive patients that were under monitoring at the UCSD VA [Veterans Affairs] Health Sciences Center in San Diego.
How did they break down by race and gender?
That was something that's masked to us. We were only concerned if they were positive or negative. So that was something that was all on the physicians' side. We didn't want that information for this study.
What would you say the clinical implications are?
Clinical value is only just to determine a lot of samples that are sent off to be quantitated. In this case, out of 100 samples, only 50 of those samples we found really needed to be quantitated, because there was a change in status of the patient. The other half really didn't need to be quantitated. It's basically at this stage of the study just showing that it would be cost effective not to send those samples out.
Has anything like this ever been done before?
Not to our knowledge. It's kind of just a synthetic study, where we just play with the cut-off value. With the HIV-1 test, no, because we're the only qualitative test out there on the market right now.
Dr. Nugent, thank you.
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