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HomeMy WebLinkAbout02042021_Dr.Rennebohn_PCR Testing_ResponseCt values at which COVID tests are positive Mark as unread Tom Locke Thu 2/4/2021 5:53 PM 1 attachment APHL-COVID1~.pdf Resent with typos corrected. Original was typed on a smart phone while overseeing a vaccination event. ________________________________________ From: Tom Locke Sent: Thursday, February 4, 2021 10:54 AM To: Rob Rennebohm; Board of Health; aunthank@co.clallam.wa.us Subject: RE: Ct values at which COVID tests are positive Dr. Rennebohm, Thank you for your thoughtful article. I apologize that I have been unable to respond in person. As you clearly recognize, CT values are an important issue in evaluating suspected false positive SARS-CoV-2 test results in those who have a low pre-test probability of infection. Unfortunately this issue has been seized upon by those who wish to discount or outright deny that we are in the midst of a poorly controlled pandemic. They wish to believe that all or most COVID PCR tests have high CT values and are thus invalid. Labs do not report CT values for a simple reason - it violates the EUA under which the tests are authorized. COVID PCR tests are licensed as qualitative assays. The labs set a positivity threshold based on characteristics of their particular platform. Attempting to turn a qualitative assay into a quantitative one by using CT as a proxy for viral load, cross contamination, stage of infection, and other deductions is fraught with error. Please review the attached article from APHL as one of many that have reviewed this issue. Urging people to discount the validity of COVID -19 testing is not helpful. Informing them of the complexities of this issue is. Tom Locke, MD, MPH Jefferson County Health Officer REPLYREPLY ALLFORWARD Mark as unread Rob Rennebohm <rmrennebohm@gmail.com> Thu 2/4/2021 1:08 PM Inbox To: Tom Locke; CAUTION: This email originated from outside your organization. Exercise caution when opening attachments or clicking links, especially from unknown senders. Hi Tom, Thank you for reading and reflecting on my writings. Like you, I have been frustrated and deeply disappointed in the Trump-promoted Narrative of Neglect and Denial—-which ignores quality scientific data and the seriousness of COVID illness. It certainly has not been helpful when people in that camp call the pandemic a “hoax” and claim that the COVID PCR test is “totally useless.” I have also been frustrated and disappointed by those at the other extreme who intolerantly avoid critical examination of data and healthy dialogue about the many clinical aspects of the pandemic. As a pediatric rheumatologists, I am steeped in the tradition of strict diagnostic and classification criteria and rigorous collection of high quality data. I have been very concerned about the low quality of data reported, regarding new COVID cases and COVID deaths, which have fundamentally been based on poorly understood binary COVID PCR results and have not involved carefully crafted diagnostic and classification criteria. I fully appreciate the limitations and problematic aspects of the Ct value associated with PCR tests. However, I disagree with the APHL decision to strongly discourage paying attention to the Ct value of positive tests. Yes, this Ct information needs to be interpreted with caution, but on balance it is far better to collect, study, and pay attention to Ct values than to ignore Ct altogether and simply and only report a binary result. For example, I worry about a 70 year old male who is admitted for myocardial infarction, has a positive Covid PCR test when screened on admission, and is placed on a “COVID ward” next to other COVID PCR positive patients. If that 70 y/o patient’s PCR test was positive at a Ct of 45 or 50, and the patient next to him has a positive test at a Ct of 22, awareness of these Ct numbers would raise concern that a patient who may have a false positive test is being iatrogenically exposed to a patient with contagious COVID. Some knowledge beyond “both being positive” would seem helpful. Ethically, I would think the 70 y/o deserves to know his Ct and that of the patient next to him. Unawareness of these Ct numbers could be responsible for the 70 y/o contracting COVID and dying from it. Likewise, when severely ill COVID patients are experiencing life-threatening “cytokine storm” for which they need bold immunosuppressive therapy, it would be helpful to know what their Ct value is at that point in time—because if it is 50, their physician can strongly consider being more bold with immunosuppression, while they would be much more hesitant if the Ct is 20. These are just two examples of how Ct values could be helpful, despite limitations involved. At the very least we should have been collecting, studying, and correlating Ct values all along, from the beginning of the pandemic, so that by now we would have far more information. Instead, we still have just binary results, and we still have very little data as to what a positive result at a Ct of 45 actually means. What scant data we do have suggests that as many as 70% of positive results at a Ct of 45 might be false positives. Why do we not have more data on this, nearly a full year into this profound epidemic? Apparently it is largely because of the APHL directive, or whoever directed the APHL to adopt this stance. The APHL warns that there are insufficient data to justify disclosure and use of Ct values. But there is an even greater dearth of data as to the clinical meaning of a binary positive test (with no Ct value provided) in a screened person who is asymptomatic (or has mild and non-specific symptoms), and yet we are making life and death decisions based on such results. Morally and ethically, and clinically, it makes far more sense to say that COVID PCR test results must include Ct results and not simply be reported as positive or negative—so that patients and their physicians can use their best clinical judgment, while carefully taking Ct limitations into consideration. I strongly disagree with the APHL decision to withhold Ct information. For one thing, that decision is not the least bit democratic; it is autocratic; and it is not based on sufficient critical thinking or healthy dialogue. I would be very willing to work with you to encourage the APHL to reconsider its November directive. Or, we could try to at least encourage the Washington state health department to reconsider its current policy. Rob Sent from my iPhone