The big story in covid should be https://www.nytimes.com/2020/08/29/health/coronavirus-testing.html

One could conclude from the article that only 10-30% of those positive are actually infectious. Basically in a nutshell one needs to ask what do you want from a test for covid. Should the primary focus be to test if one is infectious to the general population? Test if one has Covid at any level? I would presume the first question should be the prime objective. What is exactly the PCR Test? Using what most kids are now using to learn – the internet – https://www.khanacademy.org/science/biology/biotech-dna-technology/dna-sequencing-pcr-electrophoresis/a/polymerase-chain-reaction-pcr

“Polymerase chain reaction (PCR) is a common laboratory technique used to make many copies (millions or billions!) of a particular region of DNA”

In the link it goes through a sample and actually gives you a question at the end.

However the creation of the gel visualization is more complexed than they even tried to discuss. False positives were actually the issue in the beginning not false negatives. Elon Musk tweeted they had 50% false positives in the beginning – https://twitter.com/elonmusk/status/1300077893352030209?s=19

“Some of the tests we initially tried at Tesla were ~50% false positive, including some from major medical device companies. Too many testing methods were approved too quickly. Wouldn’t blame the FDA, though. Public was demanding fast test approval.”

To really highlight the complexity of PCR and the art/science blend of it you need to delv into the details – discussed in this paper – https://academic.oup.com/ajcp/advance-article/doi/10.1093/ajcp/aqaa133/5873820

In this paper they focus on not getting false negatives – which in the grand scheme of things false negatives is much worse than false positives – so typically the test are already biased to that. Key variables to understand is CT (cycle threshold – testing process) and the LoD (limit of detection)

“sensitivity of a test is largely dependent on a combination of (1) LoD of the test and (2) the distribution of viral load in the population being tested.”

“The primary aim of the study was to establish the distribution of observed CT values for each target in symptomatic patients, and to determine the proportion of patients with CT values near the LoD as an indicator of the likelihood of false-negative results due to low viral load.”

Though PCR test are the gold standard for detection – they are not focused nor can they really be used to quantify viral load. The exact level of CT is not fixed – and would seem largely dependent on the biological context of the testing. There is interpretations being made from the labs – it is not as black and white as you may think it is.

This detection but not connection with viral load could possibly explain some of the volume of asymptomatic patients and those who observe zero symptoms through the life cycle of the virus until the test show negative readings.

Amazing death count for the US even for a weekend – only 305

Ohio had a -123 death count revision….Tx lead the way at 76

Leading county Kern Ca at 12

Even though countries like Italy and Spain are resurging in confirmations deaths are not moving. One COULD conclude the virus is weaker now….or #2 more testing is confirming the virus is prevalent and most are healthy enough to defeat it….or #3 the remaining population is stronger…or #4 better ways to treat it ….I go with the combination of #2 and #4