Article · Diagnostics & Pandemic strategy · March 2020 · Episode 2/3
25 March 2020 · ~15 pages · English
Historical note. This article was written on 25 March 2020, during the first week of French lockdown. The analysis of mass testing limitations reflects the state of available test technologies and reagent supply chains at that time. Subsequent development of rapid antigen tests, pooled testing, and industrial-scale PCR shifted the testing landscape considerably.
1 · RT-PCR: principles and limits
How reverse transcription polymerase chain reaction works: RNA extraction, reverse transcription to cDNA, TAQ polymerase amplification with specific primers, exponential duplication cycles (2ⁿ). Sensitivity vs specificity trade-offs. The critical role of primer design and the risk of false negatives in early infection or after viral clearance from the nasopharynx.
2 · Serological tests: ELISA and immunochromatography
ELISA (Enzyme-Linked Immunosorbent Assay) principles: antigen coating, antibody capture, enzymatic revelation. IgM as markers of acute infection, IgG as markers of past infection and potential immunity. Cross-reactivity risks with other coronaviruses. The question of protective immunity duration — still unresolved in March 2020.
3 · Mass testing: a strategic critique
Analysis of the political demand for "test everyone" against logistical, scientific and epidemiological constraints: reagent shortages, swab production bottlenecks, laboratory capacity, workforce availability. Argument for strict confinement as the primary containment strategy, with targeted testing reserved for healthcare workers, symptomatic patients and epidemiological surveillance.
4 · Preparing the post-crisis digital infrastructure
The case for using lockdown time to build digital health infrastructure: contact tracing, serological screening databases, predictive modelling. The argument — prescient in retrospect — that the exit strategy requires data architecture, not just test volume.
This article was written at a moment when the French political debate was dominated by the question "why aren't we testing everyone?" — following Germany's perceived testing success. The author's technical explanation of RT-PCR and ELISA principles, combined with a supply chain and industrial capacity analysis, provided a counter-narrative grounded in biotechnology fundamentals rather than political positioning.
The emphasis on digital infrastructure preparation during lockdown anticipates the author's subsequent work on territorial health platforms (PREDICARE) and predictive medicine tools (TweenMe).