Covid19mathblog.com
21st day of the year in the 21st year in the 21st century….
As noted before PCR test involves a variable Cycle Threshold (CT) the higher the CT the higher “amplification” to find what you are looking for. There was no standard and that the only state requiring reporting the Ct was FL and that started in Dec. Also an important note to know which I have pointed out – Flu confirmation NEVER included asymptomatic carriers – no testing was ever done or reported on NON-symptomatic carrier. Covid is ground breaking in that PCR test done on non-asymptomatic and tracked with symptomatic.
WHO has now come out discussing normalizing the Ct https://www.who.int/news/item/20-01-2021-who-information-notice-for-ivd-users-2020-05
“WHO guidance Diagnostic testing for SARS-CoV-2 states that careful interpretation of weak positive results is needed (1). The cycle threshold (Ct) needed to detect virus is inversely proportional to the patient’s viral load. Where test results do not correspond with the clinical presentation, a new specimen should be taken and retested using the same or different NAT technology.
WHO reminds IVD users that disease prevalence alters the predictive value of test results; as disease prevalence decreases, the risk of false positive increases (2). This means that the probability that a person who has a positive result (SARS-CoV-2 detected) is truly infected with SARS-CoV-2 decreases as prevalence decreases, irrespective of the claimed specificity.
Most PCR assays are indicated as an aid for diagnosis, therefore, health care providers must consider any result in combination with timing of sampling, specimen type, assay specifics, clinical observations, patient history, confirmed status of any contacts, and epidemiological information.”
Being POSITVE with a high Ct does not necessarily make one contagious or even infected. This may also alter death reporting IF depending on PCR result to confirm death via covid vs something else.
This is not being reported to reduce the severity of the issue but to highlight the confusion to understand the truth in all this. The amount of death are so high even if HALF of the numbers are wrong this is still an issue but how one responds could be altered if the truth in the numbers were clearly understood.
A big number post again – US 4.375K deaths – with UK, Mexico, Brazil, and Germany above 1K
TX leads confirmation over CA – but CA still takes the death lead.
LA still leads all county
Big dispersion in TX confirmation.
LA county even though high – is declining rapidly in confirmation. Hopefully death will follow quickly.
