COVID 19: Black Swan or clumsy use?


COVID-19, SARS-CoV-2, screening, RT-PCR, Negative Predictive Values, False Omission Rate


Aim: “Black Swan” an unexpected and catastrophic event characterized by three conditions: the anomalous and exceptional value, the extreme impact, and predictability a posteriori. On many sides - by politicians, commentators, scientists - there have been attempts to give the COVID-19 pandemic event the meaning of Black Swan. In reality, one should wonder if the black swan was not, instead (or even), the way the epidemic was handled. In Italy, an unreasonable use of a two-step protocol - IgM/IgG anti-COVID followed by RT-PCR in the serologically positive only has caused considerable uncertainty, particularly relevant in measures for maintenance or readmission to work of health personnel.

Subjects and Methods: we calculated for each serological test the False Negative rate (FN) related to their Negative Predictive Value (NPV) and False Omission Rate (for) in different prevalence values. Since FN rate rises as prevalence increases, the resulting number might consider an estimate of health care providers admitted to caring services, despite their infectivity.

Results: This protocol could be affected by serious uncertainties arising from the analytical limitations of the tests used. To quantify this defect, we evaluated the analytical specifications of serological tests under different prevalence conditions.

Conclusion: In conclusion, although laboratory diagnostics represent a useful tool, it can only be used for epidemiological purposes and not to provide healthy pass.


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