Covid Testing
Close contacts of thousands of confirmed Covid cases are needlessly isolating due to the over sensitivity of the PCR testing process, writes Doug Casey
The ‘gold-standard’ PCR Covid test lacks transparency and gives a misleading impression of Covid infections in the community
Lockdown misery is continuing until at least March for shutdown businesses and parents of school-going children. Also affected are tens of thousands of workers who are told to restrict their movements for 14 days, if they are classified as a close contact of someone who has tested positive for Covid-19.
None of this would be necessary if the HSE was capable of coping with Covid patients. Ten months after the virus emerged in Ireland, the public health authority still hasn’t got its act together, and once again, has had to buy in treatment capacity from private hospitals.
One issue for public hospitals is staff shortages. Health workers who test positive for Covid are taken out of the line of duty, though most of them, like the vast majority of people who test positive for Covid, will never be sick enough to require hospital care.
Official data from January 1 to 25 shows that 555,000 Covid tests were processed in the period. Confirmed Covid cases were recorded at 92,900, a cumulative positivity rate of 16.7%. Covid hospital admissions in the period were 2,470 while Covid patient discharges totalled 1,980, begging the question as to how many Covid hospitalisations are seriously ill individuals.
The total number of people receiving daily ICU treatment increased from 50 on Jan. 1 to 218 on Jan. 25. ICUs have multiple admissions and discharges every day, and are the main pressure point across Ireland’s 29 acute hospitals.
Public data on public hospital capacity and utilisation is not readily available, but trolley data is i.e. the number of patients on trolleys because of a lack of available hospital beds. This shows that public hospitals in the first week of January had many more beds available than in previous years.
Such has been the success of NPHET and government propaganda that people are terrified of contracting
Covid. As hospitalisation data shows, for the vast majority of people the disease is a nuisance similar to the flu, and a large chunk of ‘confirmed’ Covid cases never even have flu-like symptoms. Far from such facts helping to ease public concerns, instead there has been ratcheting up of the panic from the start of the year.
This comes back to NPHET and the HSE’s ‘gold-standard’ testing regime for Covid. These are Polymerase Chain Reaction (PCR) tests (the most expensive type) that work by detecting DNA and RNA in biological samples. The test detects the presence of genetic material, which may or may not indicate infection. If the test detects Covid, then the person is confirmed as a Covid case even if they have no symptoms associated with the virus.
The PCR test uses amplification cycles to find viral RNA, and each cycle of amplification doubles the number of molecules in a sample. The PCR test for Covid is highly sensitive and can identify fragments of virus that have no relevance in terms of infectiousness.
PCR results provide information which is quantitative, though that data is not leveraged by Irish health authorities. The number of cycles required to flag the sample positive, known as the Cycle Threshold (Ct), is proportional to the original viral load in the sample. So the fewer cycles required to detect the virus (a lower Ct) means more infection. When the Ct is over 30 cycles, the likelihood that the person is infectious becomes very small.
According to Dr Vincent Carroll, a member of the ‘Covid Recovery’ grouping that critiques the government’s approach to the public health emergency – health authorities in Ireland have insisted that the PCR test is appropriate due to its high sensitivity, and low likelihood of missing patients with a low viral load early in the infectious period, and who will progress to become infectious.
“Unfortunately, this approach also identifies those who are in the recovery period with detectable viral genetic material, but who are no longer infectious,” says Carroll. “This group
are then needlessly isolated and cannot take part in normal societal activity such as family life, work, attention to other medical needs etc. Consider the economic consequences of needlessly quarantining many PCR positive but noninfectious cases because the test is so sensitive.”
PCR misgivings are echoed in recent US analysis of Rhode Island Covid testing from March-June 2020 with Ct scores included. This found that nearly half of the positive tests had Ct scores of greater than 32 and were therefore probably not infec tious.
Each PCR test cycle doubles the RNA copies to facilitate virus detection. So 25 cycles results in an amplification factor of x34 million, while 30 cycles results in an amplification factor of x1 billion. Yet nobody in Ireland who tests positive for Covid is ever told what the Ct score was for their test to turn out positive.
The view from Dr Carroll and his sceptical colleagues in Covid Recovery is that there should be more deployment of Antigen Rapid Diagnostic Testing. Ag-RDT does not have an amplification step so the analytic limit of de tection is two orders of magnitude higher than PCR, i.e. there must be much more virus present to be identified.
Carroll adds: “With Ct values of >30-35, the viral load is very low and at t h e se concentrations the virus is not detected by Ag-RDT. However, PCR Ct values of >35 are rarely if ever infectious. This means that the zone of infection trajectory within which Ag-RDT is sensitive, <3035, is the zone where an infected individual is actually infectious and transmitting the virus.
“Ag-RDT should therefore be considered as a momentary snapshot of infectiousness with ability to confirm a diagnosis only possible with repeat testing. With frequent Ag-RDT testing, any conversion from positive to negative could be identified before an initial PCR result has even been reported.”
Ag-RDT can complement existing PCR strategies, for example, simple and quick repeat testing of ‘weak positives’ (>Ct 30) on PCR. Ag-RDT could also be used as a screening tool to improve safety in specific situations, such as nursinghome residents, staff and visitors, healthcare workers, air travel and travel hubs, universities, professional sport, and cultural and sporting events.
Dr Carroll suggests that if the government issued home antigen tests to teachers, they could test themselves on Monday morning and feel perfectly safe going to work following a negative test. As Covid takes up to five days to manifest itself, the teacher would not have to retest unless they exhibited symptoms.
“If a teacher felt unwell, rather than self-isolate for 14 days, they could test themselves immediately and discover definitively if they have Covid or not. In addition, the antigen test is one tenth the cost of the PCR test.”
To date NPHET has shunned approval for antigen testing, though the HSE recently decided to deploy the quick and cheap solution in hospitals. T he French government has adopted a sensible approach, accepting antigen tests carried out by RocDoc and others for lorry drivers bound for French ports.