ReallyMatterVille
There are a couple of graphs up on the BC Centre For Disease Control/Provincial Health Services Authority COVID-19 website that I've been unable to ignore for the past couple of weeks.
The first is the 'positivity' rate of samples tested, which has spiked stayed high recently:
The second is the number of tests performed which have dropped recently:
So, what do these graphs mean for our true public transmission rate given the plateauing of reported case numbers coupled with our stubbornly high hospitalization numbers?
Well, as the CBC's numbers guy Justin McElroy notes, we will have to wait for more information which should be coming tomorrow:
...(S)ince Dec. 18, the B.C. Centre for Disease Control has not issued its weekly situation report, which provides additional data, including the public testing positivity rate.
Its next report will be released on Friday, two weeks after Christmas. That information will come at the same time positive tests based on transmissions happening at Christmas gatherings will be fully known.
Those who track the numbers are hopeful that additional information will provide additional clarity...
There are a couple of graphs up on the BC Centre For Disease Control/Provincial Health Services Authority COVID-19 website that I've been unable to ignore for the past couple of weeks.
The first is the 'positivity' rate of samples tested, which has spiked stayed high recently:
So, what do these graphs mean for our true public transmission rate given the plateauing of reported case numbers coupled with our stubbornly high hospitalization numbers?
Well, as the CBC's numbers guy Justin McElroy notes, we will have to wait for more information which should be coming tomorrow:
...(S)ince Dec. 18, the B.C. Centre for Disease Control has not issued its weekly situation report, which provides additional data, including the public testing positivity rate.
Its next report will be released on Friday, two weeks after Christmas. That information will come at the same time positive tests based on transmissions happening at Christmas gatherings will be fully known.
Those who track the numbers are hopeful that additional information will provide additional clarity...
But, in speaking to local mathematician and modeller Dan Coombs, Mr. McElroy tells us at least one thing that I did not personally know about testing rates in BC:
...According to Daniel Coombs, a UBC mathematician who has worked with the province on its pandemic modelling, the decline in testing can be attributed to three main factors.
The first is a sharp decrease over the holidays in testing by private organizations — which usually account for 20 to 30 per cent of overall tests — much of which is due to film productions going on pause.
The second factor is some people choosing not to get tested when they otherwise would due to personal holiday considerations — a point emphasized by Chief Health Officer Dr. Bonnie Henry last week.
But the third factor has less to do with the holidays, and more to do with the trend line B.C. was on before they began.
"Since a month ago, there's been a decline in the number of cases before testing went down," said Coombs.
"Not massive, but it has been going downward. And less cases means less contact tracing required, less testing of asymptomatic people."...
...According to Daniel Coombs, a UBC mathematician who has worked with the province on its pandemic modelling, the decline in testing can be attributed to three main factors.
The first is a sharp decrease over the holidays in testing by private organizations — which usually account for 20 to 30 per cent of overall tests — much of which is due to film productions going on pause.
The second factor is some people choosing not to get tested when they otherwise would due to personal holiday considerations — a point emphasized by Chief Health Officer Dr. Bonnie Henry last week.
But the third factor has less to do with the holidays, and more to do with the trend line B.C. was on before they began.
"Since a month ago, there's been a decline in the number of cases before testing went down," said Coombs.
"Not massive, but it has been going downward. And less cases means less contact tracing required, less testing of asymptomatic people."...
In my non-expert opinion, factors two and three are relatively self-evident, particularly for those who have been paying attention to publicly available graphs like the ones shown above. However, while I was aware of the 'private organization' testing thing, I had no idea it accounted for 20 to 30 percent of overall tests.
Regardless, clearly (and I'm not being facetious here) we really do need more clarity to know where we stand re: public rate of transmission and whether or not the current public health restrictions on gathering, etc., are effective in decreasing said transmission.
Regardless, clearly (and I'm not being facetious here) we really do need more clarity to know where we stand re: public rate of transmission and whether or not the current public health restrictions on gathering, etc., are effective in decreasing said transmission.
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Importantly, there are significant regional differences, particularly in amplitude, in the numbers buried in the graphs shown above - you can see those differences here.
Full disclosure....I know Prof. Coombs a little and might have learned about the private testing percentage directly from him if we were still riding our bikes to and from work on the pretty much the same route everyday.
Friday 6:00pm (non-)Update...Unfortunately the BCCDC report was not released as scheduled today.
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5 comments:
RossK, private tests often make up more than 20-30% of tests reported in BC. @realreporter ( Salim Jiwa) discovered this months ago by checking the number released by the feds for BC testing, and what the BC CDc dashboard said. Many times the BC number is almost double the federal number reported of BC testing. Before Christmas this was finally acknowledged by Dr.Henry and it was also acknowledged it totally skews our positivity rate to include private industry testing in with public msp paid for tests. They promised to separate the testing moving forward and then failed to do so. They only way to tell what our actual public testing numbers are is to check the daily difference reports on both federal and bc dashboards. The federal bc testing numbers are always accurate and do not include private and industry tests.
Wow - thanks for the heads-up Laila.
Hope all is well with you and yours!
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I don't understand why we even bother with the positivity rate. It's not a random sample of the BC population so what is it really telling you? If you are only testing people that might have Covid19 then you are obviously
going to get a high positivity rate. If you want to lower the positivity rate, just test one person and hope they don't have Covid.
What's really important is the number of new cases.
Gordie
Point very much taken re: the sample, particularly with all that film industry testing which likely skews towards your point about testing the same person/small group of persons over and over again.
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Symptoms include a fever, cough and difficulty breathing, according to the B.C. Centre for Disease Control. Those who think they’re infected should call a health-care professional, or 811, before visiting a doctor’s office. Testing is on demand if showing even slight symptoms.
for more information go here
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