When they are present in important blood concentration, the monoclonal immunoglobulins are known to interfere with many immuno-analyze assays. We report the case of a patient presenting a Waldenstrom macroglobulinemia, for which the determination of some parameters of the martial assessment was impossible because of the presence of IgM kappa. The analysis of analytical alarms of the automat as well as the installation of simple and fast pre-treatment protocol of the interference enabled us to quickly make a result useful for the management of this patient.