PARC Builds iPod-Sized HIV Detector

MikeChino writes "Right now it's difficult, if not impossible, to quickly detect HIV in patients living in impoverished countries. That may all change soon, though — researchers at a California outfit called the Palo Alto Research Center have built an iPod-sized handheld device that can provide an immune check-up in under 10 minutes — all with a prick of the finger. With millions of people around the world without access to a full-size laboratory, PARC's device could revolutionize the detection and treatment of HIV."

Re:This is great news

[Jenming]

In the US at least we already have access to Rapid Oral HIV Tests that give results in about 20 minutes, require no complicated equipment and are available for free in most cities.

Now if this device was cheap and easy enough to appear in nightclubs...

Re:False positives?

[RsG]

You never confirm with just one test that you have HIV. A first positive gives a reason to do a second, more thorough, test to determine if the infection is present. Also, if your T-cells are low enough to give a false positive, you probably want to find out why, as other conditions could be present.

False positives aren't as big an issue as false negatives. There's a reason why, if a person is thought to have been exposed to an HIV vector, they get multiple tests spaced out over the course of weeks or months; there is a gap between infection and lowered T-cell count. Mind you, this isn't really a new problem, or specific to the device from TFA. If the new detector is as reliable, or nearly as reliable, as current testing procedures, but cheap enough to be deployed widely in the third world, it is a very useful development.

Not an HIV detector

[LoneHighway]

This is not an HIV detector, it's a CD4 T-cell counter. If the count is below 250, it is assumed there is an immune system problem which in poor countries is likely caused by HIV. There is already a cheap test for HIV, using a mouth swab.

For monitoring patients, does not detect HIV

[toppavak]

It should be clarified that what PARC is announcing is a small flow cytometer [wikipedia.org] used to count T-cells that express the CD4 antigen [wikipedia.org], a particular subset of T-cells that is most affected by HIV. A dropping concentration of these cells in HIV+ patients' blood is a reasonable metric for the progression of AIDS. It should also be noted that the system PARC demonstrated is not a full-fledged CD4+ T-cell counter, because you also need to measure CD3 expression to tell apart CD4+ T-cells and other white cells that express CD4, like monocytes. Traditional flow cytometers do this by using two antibodies (CD3 and CD4) labelled with different colored fluorescent dyes and measuring the intensity of each color channel using a photomultiplier tube or avalanche photodiode (these are very weak signals!). The PARC prototype is a proof-of-concept that only measures CD4 expression so would very often overestimate the true concentration of CD4+ T-cells in blood.

The interesting thing here is that they've apparently been able to do away with PMTs and APDs as detectors using a method called spatially modulated fluorescence emission. Typically a very narrowly focused laser beam (a few microns or thinner) is used to excite the fluorescent label, so you get precious few photons out of it to detect (hence the need for high-gain detectors like PMTs and APDs). The idea here is to stretch out the excitation region and use a slit pattern to help in background subtraction since you can predict the locations (in time) of the fluorescence signal as it passes by the slits allowing for integration of that signal over a longer period of time with lower background than you would otherwise be able to with a standard photodiode. This also lets you mitigate the loss of bandwidth you'd get by stretching out your detection region since you can figure out which tiny spikes in signal from the photodiode go together based on the known pattern of spacings in the slit and the timings of the peaks.

Very clever! Definitely a lot more interesting than all the cytometer-on-chip microfluidics stuff that's been thrown around since the 80's to no notable success.

False sense of security?

[DJRumpy]

The only problem with this is that only after the disease has matured in the host and taken time to have a noticeable detrimental affect on the immune system, it's a little late in the game. The virus itself can spend months or even years without bringing the immune system down that low. The entire time, the infected host would be able to spread the disease, all while assuming they were 'clean' if they are not properly educated about the exact metric this test uses.

Although this test might serve a simple function of finding people who have almost moved into full blow A.I.D.S, it does not do enough to detect the disease early enough and it does not remove the need for better testing. At most, it's just a general catch all for the very obvious cases (obvious by immune system function). If anything, this would give a false sense of security.

Clueless

[joost]

a California outfit called the Palo Alto Research Center

A California outfit? Holy understatement! They invented the mouse and the desktop metaphor! They've been inventing ground-breaking stuff since the sixties!

Re:This is great news

[Anonymous Coward]

I can't even follow your angry logic to tell what you are mad about but I work in an ER and we've used the rapid oral HIV test for some time. A positive result requires an ELISA and a negative result still needs a retest at a future date. There have been no lawsuits as it is clearly just a rapid screen and the patients understand this. It is fairly cheap and much smaller than an iPOD already. This is just a press release masquerading as news.

Re:that's crap

[toppavak]

Its actually kind of true, but for the wrong reason. One of the leading causes of death in AIDS patients is chronic viral hepatitis [wikipedia.org] which destroys the liver. About 80% of cases of liver failure in AIDS patients can be directly attributable to viral hepatitis, although liver disease only accounts for 14% of the total mortality in AIDS patients. Even death due to cardiovascular disease (9% of total mortality in HIV+ patients) have been seen to correlate significantly with CD4+ T-cell count. That's not to say that there is no ART toxicity, but it still improves the survivability of the infection and increases the life expectancy of patients.

That being said, I'm pretty sure you're not going to be able to convince the /.er that feels that all "mainstream" scientists are hacks. Kind of amused he got modded interesting...