The use of polyvalent erythrocyte diagnosticum prepared on the basis of 5 polysaccharide antigens of P. aeruginosa slime, isolated from strains belonging to the most widespread serovars, makes it possible to check up the humoral response of donors after their immunization with P. aeruginosa polyvalent corpuscular vaccine with the aim of obtaining anti-P. aeruginosa donor plasma. Antibody titers, determined in the passive hemagglutination test with the use of the proposed diagnosticum and corresponding to a serum dilution of 1:320 and greater, age tentatively diagnostic, which may be indicative of P. aeruginosa in the development of purulent septic complications in patients. The use of the passive hemagglutination test with the newly developed polyvalent erythrocyte diagnosticum makes it possible to check up the specific response of patients having P. aeruginosa infection in the process of their treatment with anti-P. aeruginosa hyperimmune plasma used as a part of complex therapy.