indétectable

Indétectable is an adjective used to describe something that cannot be detected by the available detection methods or instruments. Detection depends on the sensitivity of the assay, the substance’s concentration, and the method used. A result labeled indétectable does not prove absolute absence, but that the measured quantity falls below the method’s threshold. The term appears across fields such as medicine, chemistry, engineering, and environmental science.

In medical contexts, the term is common in HIV care, where “indétectable” refers to an HIV-positive person’s viral load being below the lower limit of detection of the assay used to measure HIV RNA. With effective antiretroviral therapy (ART) and good adherence, many patients achieve this indétectable viral load, often defined as below about 20–50 copies of HIV RNA per milliliter, depending on the test. An indétectable viral load reduces the risk of HIV transmission; the U=U campaign (undetectable equals untransmittable) communicates that people with an indétectable viral load do not sexually transmit the virus under current evidence. However, indétectable is not a cure; latent viral reservoirs remain, and viremia can rebound if treatment is interrupted. Regular monitoring is required to confirm sustained undetectability.

Limitations include assay sensitivity, lab variability, and specimen quality. Indétectable is context-dependent: different tests have different detection thresholds, and a result can be indétectable in one assay but detectable with a more sensitive one. In other disciplines, indétectable can describe trace levels of chemical substances, environmental contaminants, or signals in electronic sensors that fall below detection thresholds.