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It’s generally hard to have a “false positive” in a PCR based test unless the sample was contaminated with the material trying to be detected. False negatives w
by code4tee 7y ago
It’s generally hard to have a “false positive” in a PCR based test unless the sample was contaminated with the material trying to be detected. False negatives would be much more common.
- arkades 7y agoMy understanding - from the context of criminal forensics - is that false positives from RTPCR are quite problematic, actually, due to the tendency to pick up non-target DNA that comes close enough to catch the primer. It's an issue in DNA-rich environments (e.g., nasal swabs swarming with local flora). I'm open to learning to the contrary if anyone has a decent citation on the topic.
- tlb 7y agoHuman DNA is extremely similar to any other human, but coronavirus is not very similar to other contaminants. So you need fewer samples of DNA to determine a match. Also, even a few percent chance of error in forensic DNA matching is a huge problem. If a virus test is wrong a few percent of the time it's still useful.
- nostrademons 7y agoWouldn't it be relatively similar to other coronaviruses? With coronavirus causing 15-30% of common colds and it being cold season, that's a lot of potential contaminants. [Actually, the article contains the answer to my objection: they tested for this. The test was developed by explicitly looking for primers that give positive results for known-positive COVID-19 patients but give negative results for other test subjects with common colds or other respiratory illnesses. So assuming they had enough training data, this should already be factored in, and the test should remain accurate. Posting this anyway in case other people are thinking along the same lines...]