4 ms·

It's worth nothing that this machine is very low throughput - the larger one only takes 4 samples and you have to use their proprietary disposable cartridges.

It's worth nothing that this machine is very low throughput - the larger one only takes 4 samples and you have to use their proprietary disposable cartridges. edit: as pointed out below - the largest of the machines has 80 slots and could probably do 2000/day taking around 45min-1hr/test all in Contrast that with a modern real-time PCR machine which typically has capacity for 96 samples, with some machines able to test 384 or even 1536 at a time. The tradeoff is that those machines take 2-3 hours and the lab needs to do nucleic acid extraction separately. The main advantage of this machine is that it does the nucleic acid extraction and PCR in one cartridge and in ~20 minutes. It's great for clinics and field hospitals but for an established laboratory running hundreds or thousands of tests per day, I'd wager that the standard methods are much cheaper and a bit faster overall.

mlyle 7y ago
They have bigger systems--- https://www.cepheid.com/en_US/systems/GeneXpert-Family-of-Systems/GeneXpert-Infinity https://www.cepheid.com/en_US/systems/GeneXpert-Family-of-Sy... It's pretty neat-- they have 1, 2, 4, or 16 slot things that you can slot samples into as you're ready, and they process in the background... or the big robot. It's also neat in that they have combined cartridges to do a couple of influenza detections + RSV in one rapid test (with a different color of fluorescence for each). But you're spot on in that this has a costly consumable (the cartridge)
mkagenius 7y ago
What is the false positive rates of this, if 10k people are tested everyday, can we expect 100 false positive everyday?
- killjoywashere 7y ago
  PCR tends to have great specificity and great in vitro sensitivity. The sensitivity drops off with pre-analytic errors that accumulate in real world testing (wrong collection method, wrong media, wrong swab, etc). So false negatives are the problem. The nice thing is that it catches acute infections even earlier than IgM.
- vikramkr 7y ago
  PCR tends to have pretty low false positive rates if used properly - so from a technology perspective the contribution to that would be low. Although, if they're using more innovative PCR methods, maybe there's a risk. Where I think there's room for them to introduce false positive rates (that we would not know without having access to proprietary information) is in how they design something called a primer sequence. this is a little bit of DNA that will go and find to a different little bit of DNA that's part of a larger bit of DNA. Basically it lets you target it a little bit of DNA within a larger bit of DNA. you want to make this primer so that it only will bind to coronavirus DNA but will not bind to any other DNA. It's important to design it that way because in PCR the DNA that amplifies to give you the signal is whatever that primer was able to bind it to. If you accidentally make a primer that can bind to some non coronavirus DNA (something we call off Target binding) then you would end up with false positives. There are bioinformatics tools to evaluate this and presumably the FDA and the company did some work into making sure they didn't make any mistakes when designing that, but that's what I think of first when it comes to false positives.

mlyle 7y ago

They have bigger systems--- https://www.cepheid.com/en_US/systems/GeneXpert-Family-of-Systems/GeneXpert-Infinity https://www.cepheid.com/en_US/systems/GeneXpert-Family-of-Sy... It's pretty neat-- they have 1, 2, 4, or 16 slot things that you can slot samples into as you're ready, and they process in the background... or the big robot. It's also neat in that they have combined cartridges to do a couple of influenza detections + RSV in one rapid test (with a different color of fluorescence for each). But you're spot on in that this has a costly consumable (the cartridge)

mkagenius 7y ago

What is the false positive rates of this, if 10k people are tested everyday, can we expect 100 false positive everyday?

killjoywashere 7y ago
PCR tends to have great specificity and great in vitro sensitivity. The sensitivity drops off with pre-analytic errors that accumulate in real world testing (wrong collection method, wrong media, wrong swab, etc). So false negatives are the problem. The nice thing is that it catches acute infections even earlier than IgM.
vikramkr 7y ago
PCR tends to have pretty low false positive rates if used properly - so from a technology perspective the contribution to that would be low. Although, if they're using more innovative PCR methods, maybe there's a risk. Where I think there's room for them to introduce false positive rates (that we would not know without having access to proprietary information) is in how they design something called a primer sequence. this is a little bit of DNA that will go and find to a different little bit of DNA that's part of a larger bit of DNA. Basically it lets you target it a little bit of DNA within a larger bit of DNA. you want to make this primer so that it only will bind to coronavirus DNA but will not bind to any other DNA. It's important to design it that way because in PCR the DNA that amplifies to give you the signal is whatever that primer was able to bind it to. If you accidentally make a primer that can bind to some non coronavirus DNA (something we call off Target binding) then you would end up with false positives. There are bioinformatics tools to evaluate this and presumably the FDA and the company did some work into making sure they didn't make any mistakes when designing that, but that's what I think of first when it comes to false positives.