Severe acute respiratory syndrome coronavirus 2 (SARS CoV-2) detection pitfalls

The Severe Acute Respiratory Syndrome (CoVID 19) provoked by Coronavirus 2 (SARS CoV 2) require science-based responses. The aim of this work is to assess pitfalls found during the search of viral genomes due to sampling timing, swabbing, storage, heat-infectivity inactivation and further sample processing.

According to several meta-analysis, on the day of symptom onset, the median false-negative rate is estimated to be 38%  and decreased to 20% on day 8 (3 days after symptom onset) then increased to 66% on day 21 suggesting that rRT-PCRs adds little information immediately after exposure.

RNA isolation from samples requires cautious handling using RNase-free solutions, pipet tips and glassware. The rRT PCR detection limits are estimated between 39 and 779 copies/mL but 3000 to 20.000 copies/ml for the antigen test.

External cross contamination by imperceptible splatting requires risk management integrating the Pharmacopoeias by processing at least 10 negative contiguous to 10 positive controls in each sennries of 100 tests. . For Ct >34 it was suggested no transmissible disease.

The detection of antibodies one month or later after clinical signs may confirm positivity. Lack of immune response in non-immune compromised asymptomatic people may invalidate positivity. False positive disrupts efficiency for containing infections and leads to societal anxiety undermining health workforce. Because spurious methods create confusion, each step of diagnosis requires quality-control and risk assessment, knowing that rRT PCRs amplify more than 10.000 million times the signal of 1 viral element.