Document Classification

Section Type: METHODS

Text: A cough episode that lasted > / = 7 days was considered to be a laboratory-confirmed infection by Bordetella pertussis if at least 1 of the following 5 criteria (listed in hierarchic order) was met : 1) B pertussis was obtained from nasopharyngeal culture (culture-confirmed infection) ; 2) the enzyme-linked immunosorbent assay (ELISA) IgG or IgA titer against PT in the convalescent-phase serum sample increased by at least 100 % compared with the acute-phase sample ; 3) the PT-neutralizing titers in Chinese hamster ovary assay in the convalescent-phase sample increased by at least 4-fold compared with the acute-phase sample ; 4) the ELISA IgG or IgA titer against filamentous hemagglutinin in the convalescent-phase sample increased by at least 100 % and the culture or the polymerase chain reaction assay on the nasopharyngeal aspirate was negative for B parapertussis ; and 5) the ELISA IgG PT titer in 1 of the 2 serum samples exceeded the geometric mean titer computed on convalescent sera of the children with a culture-confirmed B pertussis infection in each study group.