Abstract: The invention proposes a method for detecting and/or quantifying, in a biological sample, a cytotoxic factor, in particular a gliotoxic factor, with respect to adherent target cells, in particular macroglial cells, the toxicity of which causes the death by apoptosis of said cells. The method comprises providing an initial fraction of the sample, optionally enriched with the toxic factor by previous treatment, incubating the initial toxic factor with a reference culture medium comprising adherent target cells, and detecting and/or quantifying in the adherent target cells killed by apoptosis, by flow cytometry, at least one direct or indirect characteristic associated with the apoptotic adherent cells of the whole or part of the incubated medium, which, if it is present and/or is quantified, qualifies the sample as positive, i.e. as containing said toxic factor. The initial biological sample is preferably a urine specimen.