[A contribution to stepless antibody determination by the "enzyme linked immunosorbent assay" (ELISA) (author's transl)].

A simple method for the mathematical calculation of ELISA results is described. Using the formula (formula: see text) (Eu, En, Ep = extinction values of the unknown serum, the negative, and positive standard serum, respectively) an index value Iu is calculated for the testserum, whereby the optical density of the testserum is put in relation to the optical density of a negative and positive standardserum. Using three different ELISA test systems, the Iu values of a number of human, bovine and rabbit testsera were relatively uniform and reproducible in repeated investigations. A statistically calculated tolerance limit for the index values of negative sera can be introduced into the formula described, thus facilitating the decision "negative" or "positive" for unknown sera.