Judges in Portugal highlight “more than debatable” reliability of Covid tests

With the country assailed daily by news of rising case numbers, judges in Lisbon have described the reliability of tests being rolled out in their tens of thousands as “more than debatable”.

Indeed, they cite a study that suggests only 3% of positive tests declared by health authorities may be ‘true positives’.

A 34-page ruling on an appeal against a writ of habeas corpus filed by four German tourists ‘illegally confined’ to a hotel in the Azores over the summer leaves no doubt that a positive RT-PCR test cannot be taken on face value.

Few media sources however have touched on this aspect of the Lisbon Appeal Court ruling – and those that have have given it the scantest of mentions.

The judges’ deliberations nonetheless are loud and clear – set out over three pages.

The panel looked into the reliability of RT-PCR tests due the enforced confinement of the holidaymakers in question because one had tested positive.

Said the ruling, dated November 11: “In view of current scientific evidence, this test shows itself to be unable to determine beyond reasonable doubt that such positivity corresponds, in fact, to the infection of a person by the SARS-CoV-2 virus”.

RT-PCR tests (standing for polymerase chain reaction tests) “are performed by amplifying samples through repetitive cycles”.

“The number of cycles of such amplification results in a greater or lesser reliability of such tests. And the problem is that this reliability shows itself, in terms of scientific evidence (…) as more than debatable.”

It’s here the ruling cites a study conducted by “some of the leading European and world specialists in this material” published by the Oxford Academic at the end of September.

“At a cycle threshold (ct) of 25, about 70% of samples remain positive in cell culture (i.e. were infected): in a ct of 30, 20% of samples remained positive; in a ct of 35, 3% of samples remained positive and in a ct above 35, no sample remained positive (infectious) in the culture”.

“This means that if a person has a positive PCR test at a threshold of cycles of 35 or higher (as happens in most laboratories in the USA and Europe), the chances of a person being infected is less than 3%. The probability of a person receiving a false positive is 97% or higher”.

The judges stress that they “were unable to find any recommendations or rulings” on the number of amplifications used in tests carried out by Portuguese health authorities.

But they went on to cite a second study, published in the Lancet, that suggests “any diagnostic tests should be interpreted in the context of the effective possibility of the disease existing” before the test is actually carried out.

This is not what happens in Portugal – which logs ‘thousands of asymptomatic cases every day’, obliging them all to go into quarantine.

The bottom line is that these ‘asymptomatic positives’ may not be positives at all.

But while Lisbon’s appeal court appears to have accepted doubts raised by experts over the reliability of RT-PCR tests, DGS health authorities continue to use them – and the government and media continue to trumpet them as reasons for maintaining the current State of Emergency, which the country heard tonight may well continue beyond December 8 (see new story on main page).

To see the judges’ ruling in full click here.

To see a google translation into English click here.

Portugal Resident — 20 November 2020