From the beginning of the pandemic, the World Health Organization (WHO) insisted on the need to increase the number of tests to detect who has the virus and who does not. This would help isolate the infected and slow the spread. Imagine that your team qualifies for the Europa League and in the first round they play against Başakşehir in Istanbul. Before traveling to Istanbul, coaches should prepare by watching videos to identify the rival’s most dangerous players. If they do not identify them, by the 15th minute Robinho and Demba Ba (senegalese former Chelsea striker) have scored to put the home side 2-0 up. Opposition coaches need to detect and isolate them so that they do not spread their good game to their teammates.

Watching videos from other teams is easy these days. However, the tests to detect this coronavirus are somewhat complex. The most reliable, or sensitive, test to detect the virus uses a technique called Real-Time PCR (or RT-PCR). RT-PCR requires a more sophisticated —and less common— apparatus than that used for a «normal» PCR. Another complication is that the SARS-CoV-2 virus is single-stranded RNA (a single nucleotide strand instead of the two paired strands of DNA). Once the sample is collected and inactivated, the SARS-CoV-2 RNA needs pre-processing before going to the RT-PCR machine, and kits for such processing are expensive and in short supply. Because the RNA of the virus can be easily degraded, and because the sample preparation protocol is somewhat complex, tests for this coronavirus can produce false negatives due to poor collection or manipulation of the sample. Consequently, there are already publications that suggest taking a sizeable spit’s worth of saliva as a sample, instead of scratching with a stick in the throat or nose, to avoid false negatives ⁴. But what is a false negative?

A false negative is that you get a negative RT-PCR when you are actually carrying the virus. A false negative is thinking that you have made a bad signing who later turns out to be a top player. In 2015, Leicester City signed N’Golo Kante from France’s, a slight player who many thought would be outmuscled in the Premiership. But he turned out to be a false negative with the City fans nicknaming him the Kante twins due to his uncanny ability to be in two places at the same time. The French international midfielder even guided the East Midlands side to the unlikeliest of Premier title wins.

Another false negative turned out to be the signing of Dani Alves for Sevilla, in 2003, when he was 19 years old. He was brought by Monchi from Esporte Clube Bahía from Brazil for only 500.000€. Somewhat chunky in the shoulders, short and with his ears sticking out more than normal, nobody, except Monchi, could imagine that this player would develop into one of the best attacking right-backs of all time.

On the other hand, false positives are more improbable in the RT-PCRs of the SARS-CoV-2 coronavirus because that results from contamination of the sample and that is complicated if you make good use of the laboratory pipettes and if the person who processes the samples does not make any mistakes. The most famous false positive in football history was Carlos Henrique Raposo. He appeared to be a very elegant player, at the level of Marco van Basten or Franz Beckenbauer. In fact, in reference to the German player, he was also called Carlos Kaiser —kaiser means emperor in German—. Carlos’ problem was that he had no footballing talent whatsoever. Carlos Kaiser’s image was so good that, without seeing him play, clubs such as Botafogo, Flamengo, Puebla de México, Independiente de Avellaneda, or Gazélec Ajaccio de Francia signed him. When he joined the teams, he faked injuries to prevent him making his debut. Then he recovered and offered himself to another club to exploit the fact he looked like a footballer. When one day he was truly cornered and was about to play with Rio de Janeiro’s Bangu, Carlos Kaiser started a fight with a fan and got a red card before setting foot on the pitch. Carlos Kaiser appeared to be the perfect players; he was anything but that. Carlos Kaiser was a false positive.

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