2015 Volume 64 Issue 5 Pages 569-575
Over 18 months between October 2012 and March 2014, in 168 patients with a violent or lingering cough that needed to be differentiated from pertussis, a laboratory diagnostic tests of pertussis was performed retrospectively. To detect the pathogen, postnasal swabs were collected from all the patients for the isolation of Bordetella pertussis and the detection of DNA using the loop-mediated isothermal amplification (LAMP) assay. For serodiagnosis, the PT-IgG titer was measured in 126 patients (67 sets of paired sera and 59 single serum samples). Diagnosis of pertussis was defined as the isolation or DNA detection of B. pertussis or meeting the criteria for serodiagnosis. The diagnosis of pertussis based on laboratory test findings was made in 34 of the 168 patients (20%). The median age at their first visit was 0.9 years (17 days to 12.3 years). DNA was detected in 16 patients (47%), and B. pertussis was isolated in 9 (26%), all of whom were positive for DNA. Thirty-one patients (91%) met the serodiagnosis criteria, 18 (53%) of whom only falsely met these criteria. Among 7 of the 18 patients, who were unvaccinated young infants (aged 17 days to 3 months), 6 showed a decrease in the antibody titer in paired sera and one vomited after coughing caused by pyloric stenosis. These 7 patients were considered to have falsely met the serodiagnosis criteria owing to the transplacental transfer of maternal antibodies. Pathogen detection is more reliable for the diagnosis of pertussis based on laboratory test findings, with the LAMP assay being convenient, rapid, and sensitive for this purpose.
