How can you avoid false positive and false negative results (inherent to the RT-PCR technique)?

Several commercial parties have developed molecular biological methods based on the reverse transcriptase quantitative PCR (RT-qPCR) into assays for detection of viral genes in different environments. In the “Plus/Minus” test, samples and controls (distilled water) are measured, after which a positive or negative result is calculated based on differences in signal between the samples and controls. When applying the “Plus / Minus” test for detection of SARS-CoV-2 coronavirus genes, we observed part of the false positive and negative signals, demonstrating that the method used is valid.