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A lot of people have requested us to measure the case fatality rate (CFR) and disaggegrate by age group in our #COVID19PH dashboard ( http://bit.ly/COVID19PHdashboard)
Let me explain in this thread why we don't #epitwitter
Let me explain in this thread why we don't #epitwitter
1/ The crude way of measuring CFR is # of deaths / # of cases. CFR indicates the severity of the disease. See ref from Gordis Epidemiology below
So it should be easy to calculate CFR, right, and specify by age, given that our dashboard gives a breakdown of cases & deaths by age?
So it should be easy to calculate CFR, right, and specify by age, given that our dashboard gives a breakdown of cases & deaths by age?
2/ Not so fast. Let's talk about the denominator first. The denominator is limited significantly by the Philippines' testing capacity - still hovering around 1K+ samples per day (and remember, positive cases are tested more than once until they recover!)
See progress as of Apr 4
See progress as of Apr 4
3/ But that's only part of the story. Our current testing algorithm prioritizes potentially severe / high risk cases (see below https://www.deped.gov.ph/wp-content/uploads/2020/03/DOH-DM-Amendment-To-Department-Memorandum2-020-0108-Entitled-GuidelinesF-or-Management-Of-Patients-With-Possible-And-Confirmed-COVID-19.pdf). Even if we assume that the "massive testing" strategy of all PUIs / PUMs by April 14 is going to be perfectly implemented...
4/...the denominator will still be restricted to a small subset of cases. See figure below from https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30243-7/fulltext
From the WHO-China Joint Mission Report, 4 out of 5 #COVID19 cases (80%) will present with mild to moderate symptoms. https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf&ved=2ahUKEwjbzf33wdDoAhWJF6YKHVd7BUQQFjAAegQIBxAC&usg=AOvVaw1gO_RTfaIWQuEkjdvq_O7i
From the WHO-China Joint Mission Report, 4 out of 5 #COVID19 cases (80%) will present with mild to moderate symptoms. https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf&ved=2ahUKEwjbzf33wdDoAhWJF6YKHVd7BUQQFjAAegQIBxAC&usg=AOvVaw1gO_RTfaIWQuEkjdvq_O7i
5/ Which brings me to a sidebar - no public health professional believes in the version of #masstestingnow where all or a majority of Filipinos will be tested. Stop watching Kdramas & comparing 
's health system to 
. Even with our best efforts, we cannot feasibly do that.
's health system to . Even with our best efforts, we cannot feasibly do that.
6/ What we need is to be STRATEGIC about testing. Continue scaling up labs, sourcing PCR kits wherever we can, while PROPERLY implementing testing protocols. What angers me about VIP testing is that it worsens the backlogs for everyone else, and messes up the definition of tested
7/ Ok, now for the numerator (deaths). The DOH is taking a LONG time to report deaths, longer than reporting cases (see my histogram below). This means that there are deaths that may have happened already, but are not yet reported. Thus, we are undercounting the numerator.
8/ As you can see, it's really not that simple. As a measure of severity, CFRs during outbreaks, especially for novel infections like #COVID19, are full of noise. @voxdotcom did a comprehensive piece on the literature so far in richer countries. https://www.vox.com/2020/4/1/21203198/coronavirus-deaths-us-italy-china-south-korea
9/ So, how do we measure CFR accurately then? An idea floated by some experts (and I concur if we have time) in our IATF TWG discussions is to conduct a smaller community study with a more random sample of the population, and extrapolate values from there. https://www.nejm.org/doi/full/10.1056/NEJMp2002125
10/ For our forthcoming white paper on the epidemiological and economic modelling of #COVID19, we assessed severity (as a parameter in our models) based on a method proposed by Ghani and others (2005) based on Kaplan-Meier survival curves. https://academic.oup.com/aje/article/162/5/479/82647
11/11
The discussion on the CFR of #COVID19 seems to be a lively discussion within the #epitwitter community. For example, I refer you to a series of recent commentaries on the Lancet.
Start here https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30195-X/fulltext and follow the Linked Articles in the end.
RT away!
The discussion on the CFR of #COVID19 seems to be a lively discussion within the #epitwitter community. For example, I refer you to a series of recent commentaries on the Lancet.
Start here https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30195-X/fulltext and follow the Linked Articles in the end.
RT away!
