But, because positive people are almost always retested here we can actually examine this question more robustly. Of the 226 positive results, one was later retested and found to be a false positive!pic.twitter.com/kw8GgKdu4Q
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But, because positive people are almost always retested here we can actually examine this question more robustly. Of the 226 positive results, one was later retested and found to be a false positive!pic.twitter.com/kw8GgKdu4Q
To calculate test specificity, we take TN/(TN+FP) = 607333/(607333+1) = 99.99984% To put it another way, very roughly 1 false positive test per million tests done
This very quickly and easily shows why the idea that most COVID-19 positive tests are false positives is simply misinformation and mathematically impossible
If 1%, or even 0.1%, of all tests done were false positives, we would expect to have seen 1,000s of positive COVID-19 results in NSW in the last month rather than a few hundred
I find this shocking in Texas, where our positivity rate has never, to my recollection, been below 5%, and usually hovers between 8 and 15%.
I don't think we've been above 2% for any 7-day period ever in NSW 
Serious Q - How do we reconcile results like this with claimed specificity from the manufacturer? For example, below is a test I took in NYC with NPA of 95.6%. Is Australia using a different test?pic.twitter.com/i9ZfoiJHDa
The standard you are comparing your test against determines the results as does the test itself. In this case, the two negative results that turned out positive with the xpert test might have been "false-negative" before.
Amazing data. You are clearly best in class if true. You should get your data and methods peer-reviewed and published in The Lancet to put a stop to this "false-positive" guff, like this article ...https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30453-7/fulltext#figures …
False positives are very uncommon but a person can be reported positive without being infected due to contamination in the lab. This is a true positive for the test but an erroneous result for the patient. Contamination is more likely if there are many positive samples in the lab
That's a complete non-sequitur. It makes no difference. Even if it was true for every sample in NSW, it would still only be happening once every 100,000 tests or so
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