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“Fear of the False Negative Test” for SARS-COV-2 virus, cause of COVID-19: Medpage Today (an article review, followed by a long and fervent rant).

2020-04-21

klee flower by cocoparisienne courtesy of pixabay.com

Medpage today has an article published April 20 titled “Fear of the False Negative COVID-19 test” which describes concerns over the false negative rate of the virus antigen nasopharyngeal swab test, especially for healthcare providers.  The article states that, with a 10% prevalence of truly infected COVID-19 patients, out of a million healthcare providers, 40,000 will show false negative tests.  This is a serious problem both for providers and patients, and the first statement in the article underestimates the extent of the problem.

In fact, the rate of positive tests in patients later confirmed to have COVID-19 is only 70-80%.  A Chinese study of 51 patients who had abnormal chest CT, only 71% (36/51) had positive RT-PCR nasopharyngeal swabs at the first go.  One patient required four swab tests to isolate the virus.  From the CT study:

50/51 (98%) patients had evidence of abnormal CT compatible with viral pneumonia at baseline while one patient had a normal CT. Of 50 patients with abnormal CT, 36 (72%) had typical CT manifestations (e.g. peripheral, subpleural ground glass opacities, often in the lower lobes and 14 (28%) had atypical CT manifestations.

From the study’s conclusions:

In our series, the sensitivity of chest CT was greater than that of RT-PCR (98% vs 71%, respectively, p<.001). The reasons for the low efficiency of viral nucleic acid detection may include: 1) immature development of nucleic acid detection technology; 2) variation in detection rate from different manufacturers; 3) low patient viral load; or 4) improper clinical sampling. The reasons for the relatively lower RT-PCR detection rate in our sample compared to a prior report are unknown. Our results support the use of chest CT for screening for COVD-19 for patients with clinical and epidemiologic features compatible with COVID-19 infection particularly when RT-PCR testing is negative.

Compared to rates of positive tests done by bronchoalveolar lavage (fluid taken from deep in the lungs by bronchoscopy, a tube inserted down the throat into the lungs to observe to bronchi), with a positive rate of 93%, the nasopharyngeal swab is inadequate for making a diagnosis.  This explains why the Chinese decided to include abnormal chest CT findings as a criterion for diagnosis of COVID-19 cases.

A patient who presents with cough, fever, chest pain, and shortness of breath is likely to have viral bronchitis or pneumonia.  If the test done by nasopharyngeal swab is negative, the patient may be falsely concluded to have influenza (or an influenza-like illness caused by another virus or a bacterium).  Tests can be performed for the influenza virus, cold coronaviruses, and bacteria, and if these are negative, further suspicion may fall upon the new virus– but this state of affairs will lead to patients not being adequately isolated and not included in case counts.

More seriously, if the patient is a healthcare provider, and they go back to work, they may wind up infecting many patients who would not otherwise be exposed.

The only solution is to presumptively isolate all patients who have symptoms consistent with influenza-like illness.  This may perhaps have been the best course of action even if the new virus were not known to exist, since it would lead to patients not being exposed to other contagious illnesses that could have equally adverse effects clinically.

The clinician’s learning curve for this viral pandemic is steep, indeed.  We need to take instruction from the Chinese, who, despite their suspicious behavior in regard to case counts (which subject is open for discussion, either way), have provided us with a great deal of information about the disease, making diagnoses, and ways to combat its spread.  We (the editorial “We”) cannot condone totalitarian behavior by the Chinese government.

We must seek voluntary agreement to isolation, surveillance, and control because agreement is essential to win this fight.  We can only obtain voluntary compliance with strict measures by radical transparency and protection of the identities of those who are affected.  This is seen with the South Korean model, where they have gained the upper hand and are continuing the fight with almost complete buy-in of the entire population of South Korea.

We call for all Americans to be given access to “smartphones” that are programmed with infection tracing, news apps, and control measures.  This includes notification of all significant developments in news of the campaign and information about confirmed cases that have “crossed the path” of the smartphone owner so they can be fully informed and take precautions to prevent illness or inform disease-control teams if symptoms arise.

We also demand that tests be made available to all Americans, both acute (virus RNA detection by nasopharyngeal swab or sputum analysis) and chronic (serum antibodies or serology) as soon as is possible.  If it appears to be necessary, the president must invoke the Defense Production Act to order private industry to develop and market testing supplies and equipment.  A small step in the right direction was announced yesterday: an order to produce 20 million swabs for use in the virus detection test kits.

Much greater efforts are needed if we are to rescue the economy and return the US to a leading place among the nations of the earth.  I/we call upon all Americans to “vote the bums out” and begin a program of radical restructuring that will work to end the obfuscation, corruption, and incompetence of the current administration led by a sociopathic, narcissistic, nepotistic con-man.  We can do no less for our fellows, especially those who have been left behind and are being mowed down by the pernicious new virus.  Members of minority groups, including Native Americans, African-Americans, Caribbean-Americans, Asian-Americans, and Latin Americans, have been discriminated against in the past and are now being affected in greater numbers by this virus.  I/we call upon all Caucasian-Americans (European and British) to stand together with your fellow Americans of color to defeat the seditious conspiracy of plutocrats who have seized control of this country and have been running it into the ground since their Electoral College victory in 2016.

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