Starting from the generalized perturbation formulations in the neutron field obtained from the importance conservation principle, perturbation expressions for any desired order relevant to measurements in the nuclide field are derived by analogy. Their use is proposed for correlating isotopic analyses of samples irradiated in fast power reactors with the nuclear parameters. In particular, information on capture and fission cross sections of fissile and fertile materials may be obtained and effectively used in a consistency approach. A numerical example is given relevant to first- and second-order perturbation terms, which illustrates the applicability of the method.