WHO Issues New Guidance for Determining PCR Test Results

by Marco Cáceres

Published February 21, 2021 | Opinion

There is a scene in the 1982 movie Star Trek II: The Wrath of Khan, in which Captain Kirk is asked by Lieutenant Saavik, “The Kobyashi Maru, sir. … On the test, sir, will you tell me what you did? I’d really like to know.” Dr. McCoy interjects: “Lieutenant, you are looking at the only Star Fleet cadet to ever beat the no-win scenario.” Saavik: “How?” Kirk: “I reprogrammed the simulation so it was possible to rescue the ship.” Saavik: “What?”^{1 2 3}

At that point, Kirk’s son, Dr. David Marcus, grins in disbelief and says, “He cheated.”¹ Kirk responds…

I changed the conditions of the test. I got a commendation for original thinking. I don’t like to lose.¹

On Jan. 13, 2021, the World Health Organization (WHO) issued a new guidance on the polymerase chain

reaction (PCR) nasal swab test commonly used to detect the presence of the SARS-CoV-2 virus in people. The WHO guidance states that “careful interpretation of weak positive results” of each PCR test given is needed, given that the cycle threshold (CT) “needed to detect the virus is inversely proportional to the patient’s viral load.”^{4 5 6}

In other words, the greater amount of the virus (viral load) a person has in their body the lower the CT needs to be set at to detect the presence of the virus. The lower amount of the virus in a person the lower the CT need to be to detect the presence of the virus. The CT refers to the number of times a sample is amplified by a PCR machine, or thermocycler, to get a result. The CT levels at which many manufacturers of thermocyclers recommend they be set at is under 40.^{6 7 8 9}

Some scientists such as virologist Juliet Morrison, PhD of the University of California, Riverside believes any CT over 35 is too sensitive. “I’m shocked that people would think that 40 [cycles] could represent a positive,” said Dr. Morrison, who thinks a more reasonable CT cutoff would be 30 to 35.^{7 10} An article in The New York Times noted, “The CDC’s own calculations suggest that it is extremely difficult to detect any live virus in a sample above a threshold of 33 cycles.”¹¹

The WHO guidance adds:

Where test results do not correspond with the clinical presentation, it recommends that a new specimen should be taken and retested using the same or different NAT technology.^{4 5}

PCR Test Results Only One Fact to Consider in Diagnosing Coronavirus

The WHO also cautions health care providers not to rely only on the results of a PCR test to detect the SARS-CoV-2 virus, but to “consider any result in combination with timing of sampling, specimen type, assay specifics, clinical observations, patient history, confirmed status of any contacts, and epidemiological information.” In other words, just because a PCR test comes back positive for SARS-CoV-2 should not be the sole consideration for determining if someone has the virus. That determination, according to the WHO, should be based on an analysis of a broader range of factors. The WHO describes PCR test results as an “aid for diagnosis,” which suggests they are not the only piece of evidence that should be used to diagnose COVID-19.^{4 5}

With its new guidance, reportedly the WHO is simply attempting to remind those who administer and evaluate the results of PCR tests to “use tests with the proper instructions to ensure accurate results.”¹² Apparently, the WHO had received 1o reports of problems related to PCR tests. According to Reuters:

The WHO confirmed after investigating that the tests were not being used in compliance with instructions provided by the manufacturers. Laboratories faced problems when they did not apply the recommended “positivity threshold,” which can result in false negative or false positive results.¹²

The extent of the improper use of PCR tests by laboratories is unclear. There are questions, such as: were many laboratories, for example, consistently running PCR tests at higher CTs than recommended by the thermocycler manufacturers? Virologist Ian M. Mackay, PhD of the University of Queensland in Australia says that laboratory technicians run PCR tests at 40 to 50 CTs.¹² Another question: were many laboratories solely using PCR test results to determine whether or not someone is deemed to be a positive coronavirus case, rather than considering the broader approach spelled out in the WHO”s guidance?

All the WHO guidance suggests is that there was a problem with the way some laboratories were using PCR tests prior to Jan. 13 and that the guidance was part of an effort to address and correct it. There is no way to know how serious or widespread the problem was with PCR testing for COVID-19 cases yielding inaccurate COVID-19 test results.

Coronavirus Cases Start to Decline Sharply in U.S. and Around the World

What is interesting is that within days of WHO guidance being issued, the number of new coronavirus cases reported in the United States began to markedly decline. The New York Times reported on Jan. 22 that, “In recent days, coronavirus cases have been dropping steadily across the United States.”¹⁴ The newspaper stated on Feb, 17 that 70,176 new coronavirus cases were reported in the U.S. and, on Feb. 18, said, “Over the past week, there has been an average of 77,665 cases per day, a decrease of 43 percent from the average two weeks earlier.”¹³

On Feb. 1, the WHO announced at a press conference that coronavirus cases were dropping around the world.¹⁵ WHO director general Tedros Adhanom Ghebreyesus said:

For the third week in a row, the number of new cases of COVID-19 reported globally fell last week. There are still many countries with increasing numbers of cases, but at the global level, this is encouraging news.¹⁵

On Feb. 10, CNN reported that the WHO announced there had been a 17 percent decline from the previous week in the number of the coronavirus cases and the lowest number of cases since the week of Oct. 26, 2020.¹⁶

On Feb. 15, NBC News reported that, in the previous two weeks coronavirus cases had declined to “varying degrees in all 50 states, as well as in Washington, DC, Puerto Rico and the Northern Mariana Islands, and added:

Ten states and Puerto Rico saw a slight decrease between 10 and 25 percent. Forty states, plus the district and the Northern Mariana Islands, experienced a more significant decrease of 25 percent or more.¹⁷

On Feb. 17, The Atlantic published an article titled “COVID-19 Cases Are Dropping Fast. Why?”¹⁸ Staff writer Derek Thompson, offered four reasons for the rather sudden downward trend…

1. Behavior: Maybe Americans finally got the hang of this mask and social-distancing thing.
2. Seasonality: The coronavirus was perhaps destined to decline this time of year.
3. Partial immunity: Is the virus running out of bodies?
4. Vaccines: The shots work.

But worldwide, simultaneously?

In an interview CNN’s “Fareed Zakaria GPS” on Feb. 14, former CDC director Tom Frieden, MD said:

I don’t think the vaccine is having much of an impact at all on case rates. It’s what we’re doing right: staying apart, wearing masks, not traveling, not mixing with others indoors.¹⁸

I wonder. Might there not be something else at play here?

---

Click here to view References:

  Captain Kirk, CDC, Centers for Disease Control and Prevention, CNN, COVID-19, CTs, cycle threshold, David Marcus, DC, Fareed Zakaria GPS, Ian M. Mackay, Juliet Morrison, Kobyashi Maru, Marco Cáceres, NAT technology, National Vaccine Information Center, NBC News, Northern Mariana Islands, NVIC, PCR tests, polymerase chain reaction, Puerto Rico, Reuters, Riverside, Saavik, SARS-CoV-2, Star Trek II: The Wrath of Khan, Tedros Adhanom Ghebreyesus, The Atlantic, The New York Times, The Vaccine Reaction, thermocyclers, Tom Frieden, University of California, University of Queensland, Washington, WHO, World Health Organization