Naïve CFR
After the SARS epidemic, a paper was published in the American Journal of Epidemiology by Ghani et al., Methods for Estimating the Case Fatality Ratio for a Novel, Emerging Infectious Disease, where they demonstrated that this common method to estimate the CFR was severely flawed. The authors call it a “naïve estimate:”
naïve CFR = deaths / cases
They noted this method is “clearly easier to describe to policy makers and the public” however it exhibits “considerable bias.” In the case of SARS in Hong Kong in 2003, between 2 April and 21 May it “falsely suggested a rise in the case fatality ratio” by 5x, from 2% to 11%. See the “naïve CFR” curve labelled “simple estimate 1” in their figure 3a:
In reality the true observed CFR has been about 13% during this period of time. The naïve CFR was severely inaccurate due to “simply an artifact,” a lag: “the final outcome for patients [death or recovery] lagged behind their identification by approximately 3 weeks.”
From
The Case Fatality Ratio of the Novel Coronavirus (2019-nCoV)
06 Feb 2020
Keywords: epidemiology coronavirus wuhan
No comments:
Post a Comment