Critically Examining COVID Epidemiologic Data
Interpreting COVID Cases, COVID Hospitalizations, and COVID Deaths
An Exercise in Critical Thinking and Healthy Dialogue
On November 10, 2020 CNN reported that, during the preceding week, the following was occurring in the USA :
- 119,238 new cases of COVID were occurring per day (on average).
- “Soon, there will likely be 200,000 new cases occurring per day.”
- 59,000 new COVID hospitalizations were occurring per day.
- More than 1000 new COVID deaths were occurring per day.
CRITICAL EXAMINATION OF DATA:
COVID-19 can be life-threatening and life-taking, especially in the elderly and frail. A tragic number of people have died from COVID-19. The above CNN report further heightens fears.
However, in the tradition of rigorous science and disciplined practice of medicine, it is imperative to critically examine such data— to determine the scientific quality of the data and whether they understate, accurately state, or overstate the threat we face. It is not scientific to accept data at face value, without thorough critical analysis. Included in this critical examination is the need to pay attention to language and insist on careful, accurate use of language.
This article is intended to facilitate healthy, respectful, evidence-based dialogue about COVID-related epidemiologic data. The purpose of the article is to emphasize what questions need to be asked about the quality of the data being collected and reported. The goal of the article is to raise the necessary questions, not necessarily answer them. However, it is hoped that these questions will be answered by those who are leading our nation’s response to this epidemic (e.g., the USA Task Force on COVID, the CDC, Johns Hopkins University Bloomberg School of Public Health, WHO, the University of Washington Institute for Health Metrics and Evaluation, and the Gates Foundation).
To determine the quality and meaning of reported data, such as that reported by CNN on 11/10/20, it is necessary for physicians, public health officials, politicians, and the public to ask the following questions:
- What definition of a “new COVID case” is being used in this reportage? What criteria must be fulfilled for an event to be declared a “new COVID case”?
- Do these “119,238 new SARS-CoV-2 infections” occurring per day represent people who have been confirmed to be currently and definitely infected with the SARS-CoV-2 virus? Or do these 119,238 “new COVID cases,” more accurately, represent simply the number of “positive COVID tests” that have been recorded? This distinction is important, because a “positive COVID test” may or may not mean that the tested person has truly been infected with the COVID-19 virus [2-34]; and, even in the case of a true positive, may or may not mean that the person is capable, at the time, of infecting others [3, 8, 24-26].
- Is a “positive COVID test,” alone, sufficient to be counted as a “new case?” That is, can asymptomatic people who happen to have a “positive COVID test” be counted as “new cases?” Or to be counted as a new case, must a person be both “COVID test positive” and have COVID symptoms? If so, what minimum number and types of symptoms must be present (and when, chronologically) for a person to be considered to have “COVID symptoms?”
- What criteria must be fulfilled to declare a person’s COVID test to be positive? Does a “positive COVID test” need to be a PCR test, or could it be one of the less reliable rapid antigen tests?
- For PCR tests used, what cycle threshold (Ct) “cutoff” is being used for declaration of a positive test?” For a detailed explanation of Ct values, see companion article entitled, The Importance of Knowing the Ct Value at which a COVID PCR Test is Positive—LONG VERSION, and REFERENCES [2-34]
- For PCR tests that are positive only after 37 or more amplification cycles (i.e., at a Ct of 37 or higher), are we sure that that positivity is truly and always due to definite COVID infection, especially in asymptomatic or minimally and non-specifically symptomatic people who were tested as part of a screening (surveillance) process?
- What is the false positivity rate of COVID PCR tests? Is the false positivity rate higher when the test is used in a surveillance setting, as opposed to a hospital/ICU setting? Is the false positivity rate higher in people whose test is only weakly positive (Ct of 37 or 40, or 45), than in people whose test is strongly positive?
- Since the beginning of the COVID pandemic, results of COVID PCR tests have been reported only as positive or negative, without any mention of the Ct value at which the test was positive—i.e., without any mention of how strongly or weakly positive. Has that been a wise policy?
- Of the recent/current COVID test positive “new cases” what was the breakdown regarding the degree of test positivity—what percentage were positive only at a Ct of 37 or higher? What percentage were positive only at a Ct between 30-34? What percentage were positive at a Ct less than 30; less than 24; less than 20; less than 15; less than 10? Do these Ct statistics not matter? Does it not matter whether the test was strongly positive or only very weakly positive?
- Of the “new cases,” what is the breakdown regarding degree of symptoms—what percentage were asymptomatic, mildly symptomatic, moderately symptomatic, severely symptomatic, and specifically symptomatic of COVID?
- When a “positive” COVID test result is reported to the State Health Department and then to the CDC and the Johns Hopkins Bloomberg School of Public Health database, who has filled out a data record form on that person and how frequently and accurately does it contain all the above-mentioned clinical information, including details about symptoms and the Ct at which their test was positive? Or is there often little or no clinical information provided, other than the fact that the person “had a positive COVID test result?”
- The World Health Organization (WHO) and many government health ministries have encouraged diagnosis of SARS-CoV-2 infection (COVID) on the basis of a single positive PCR result, even in asymptomatic persons without any history of exposure.  For example, WHO has defined a “confirmed case” as a person with a positive test result, “irrespective of clinical signs and symptoms.”  Is that the policy that is being applied to the “new case” counts being currently reported in the USA?
- In the USA, the Council of State and Territorial Epidemiologists (CSTE) has developed a more appropriate and nuanced “COVID-19 Interim Case Definition,” which was approved by the CDC in August 2020.  To what extent are the criteria recommended by the CSTE being strictly applied in the current collection, determination, and reportage of “new COVID cases” in the USA? Of the 119,238 daily “new cases” reported on 11/10/20, what percentage of them fulfilled strict CSTE criteria for presence of “confirmatory” vs “presumptive” vs only “supportive” evidence for designation as a “new case.” If a person had a “positive COVID test,” but other details needed to make an accurate CSTE designation were missing, was such a person, nevertheless, entered as a “new case,” or were such people designated as “possible new case, but available information is insufficient” and not included in the case count, or included as a separately reported “possible case”?
- Bear in mind that even the more demanding “case definition” recommended by the CSTE does not include any mention of the extent to which a COVID test is positive—i.e., Ct values are not considered. According to the CSTE recommendation, a person whose PCR test for COVID is positive only at a Ct of 40, or even 45 (very weak and questionable positivity) would be considered to have “confirmatory laboratory evidence” of COVID. Does that represent a scientifically sound decision?
- Likewise, the case definitions recommended by the CDC and WHO do not include any mention of the extent of COVID test positivity (e.g., Ct values). Is this wise?
- To what extent have efforts been made to ensure that “new cases” are not counted more than once? For example, if a previously known “COVID positive” person has had several positive follow-up re-tests (to document possible ongoing infectivity) is each positive re-test included in the “new case” count? How is such duplicate counting prevented?
- If 119,238 “new cases” were noted on a particular day in the USA (on 11/9/20, e.g.), how many people were tested on that same day? It turns out that approximately 1.5 million tests were performed daily during the week before 11/10/20. What was the breakdown, regarding percentage of those 119,238 that were positive only at a Ct greater than 30? What percentage were positive at a Ct of 30 or less?
- How many false positives would be expected, if 1.5 million asymptomatic or minimally and non-specifically symptomatic people were tested, as part of a mass screening/surveillance campaign? Since we currently do not know what the false positivity rate is in the mass surveillance setting, we do not know how many of the 1.5 million would be expected to have a false positive result.
- During a given week, to what extent is a portion of a “rising daily new case count” simply a reflection of a rising number of people being tested?
- Regarding the reported number of “new COVID hospitalizations,” were all these patients hospitalized primarily because of COVID illness, or were some (what percentage?) simply patients who were hospitalized for other reasons and happened to have a positive COVID test (how strongly or weakly positive?) when routinely screened at the time of admission?
- Likewise, regarding new “COVID deaths,” what criteria were strictly applied in each case to accurately determine whether a patient truly died of COVID, as opposed to dying from some other cause, but having a “positive COVID test” (again, how strongly or weakly positive?) or even just COVID exposure? How complete and accurate has information on these “COVID death” certificates been? On a death certificate, does the mere mention of a positive COVID test, or exposure to someone with COVID positivity, mean that that death is automatically included in the national “COVID death” count? To what extent have those who complete death certificates been told that they must list “COVID test positivity” and “COVID exposure” on a death certificate (if such positivity and exposure have occurred), even if COVID was not considered the cause of death or even a minor contributing factor? In past years, have “influenza test positivity” or “exposure to influenza” been listed on death certificates, if influenza was not considered one of the main causes of death, or even a minor contributing cause? What have the rules been, regarding this issue, and how uniformly have rules been applied.
- Regarding people who definitely died of COVID, what treatment did they receive? Did they receive prompt, timely, appropriately aggressive immunosuppression, if they had evidence of hyperinflammation/cytokine storm? What percentage of true COVID deaths could have been prevented with application of a different, more aggressive and compulsive treatment approach? [37,38] (See companion articles on Treatment of Severe COVID Illness.)
- In short, do the above CNN-reported data represent solid, quality data that were collected and interpreted in a scientifically sound fashion and accurately reflect reality—and might even understate the threat we face?
- Or have the COVID data collected and reported (at least in the USA) been of much lower scientific quality than has been assumed.
Without answers to the above questions, it is difficult to know what a “new COVID case” means, what a “rising new case count” means, or what a “rise in COVID hospitalizations” and a “rise in COVID deaths” mean.
The quality of data, regarding “new COVID cases,” “new COVID hospitalizations,” new COVID ICU admissions,” and “new COVID deaths,” depends, fundamentally, on:
- The quality, reliability, interpretation, and wise use of the COVID tests upon which these data are based; and
- Disciplined and uniform use of carefully constructed diagnostic and classification/stratification criteria for “COVID case,” “COVID hospitalization,” and “COVID death.”
- The extent to which patients with severe COVID illness are optimally treated.
Furthermore, the quality of COVID-related public health policy and public understanding of COVID depend on the quality of the above data.
If most COVID tests are performing 37 or more cycle amplifications in their effort to detect presence of viral material; if most positive tests (especially in surveillance testing) are positive only at a Ct of 35 or greater; if people with a positive test at a Ct of 37 or 40 are, in fact, not contagious; and if the currently unknown incidence of false positive tests (especially in the surveillance setting) is higher than heretofore appreciated; then, the currently reported COVID data may be greatly inaccurate, or at least excessively alarming—particularly “new case” data that have been generated primarily through mass screening of increasing numbers of asymptomatic and minimally (and non-specifically) symptomatic people.
Similarly, if Ct values and uniform criteria have not been strictly applied to reported data on COVID hospitalizations and COVID deaths, these data need to be viewed with caution. Finally, if treatment of patients with severe COVID illness has been suboptimal, COVID ICU and death data will be misleading.
We all have an obligation to make certain that fundamental principles of science, medicine, clinical care, and clinical/epidemiological research are being rigorously followed in the collection, interpretation, and reporting of COVID cases, COVID hospitalizations, and COVID deaths.
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Rob Rennebohm, MD
About the Author: https://notesfromthesocialclinic.org/about-me/