Since April 1993 in Finland and March 1994 in Switzerland, polymerase chain reaction (PCR) has been used routinely nationwide for the diagnosis of pertussis. Nasopharyngeal specimens from 3794 patients suspected of having pertussis and 1125 controls were tested. Finnish and Swiss assays found 23% and 36% of clinical specimens positive, respectively. PCR showed a higher incidence of pertussis infection among 1- to 6-year-old children in Switzerland than in Finland (P < .001). This difference may be due to the booster dose of vaccine given at 2 years of age in Finland but not in Switzerland. In Finland, PCR-confirmed asymptomatic cases were more common among children <7 years old than in older children (P < .001), whereas older children tended to have symptomatic infection. The use of PCR markedly improves the diagnosis of pertussis and opens new perspectives for epidemiologic and vaccine efficacy studies.

ABSTRACT. Objective. To assess the diagnostic sensitivity and specificity of a Bordetella pertussis polymerase chain reaction (PCR) assay using nasopharyngeal (NP) specimens from subjects with cough illnesses participating in a large pertussis vaccine efficacy trial.Design. From 1991 to 1994, we conducted a large pertussis vaccine efficacy trial in Germany to determine the efficacy of the Lederle/Takeda acellular pertussis component diphtheria-tetanus toxoids in comparison with the Lederle whole-cell component diphtheria-tetanus toxoids vaccine. In the final year of the follow-up period of this trial, a second NP specimen for PCR, in addition to a culture specimen and blood for specific serology (enzyme-linked immunosorbent assay), was collected by use of a Dacron swab in subjects or family members with cough illnesses >7 days duration or in subjects with exposure to a cough illness in a household member to establish a diagnosis of B pertussis infection. Oligonucleotide primers (pTp1 and pTp2) that amplify a 191-bpsized DNA fragment from the pertussis toxin operon, which is specific for B pertussis, were used. The PCRamplified products were visualized by dot blot analysis followed by hybridization with a digoxigenin labeled probe and rated as 1؉, 2؉, or 3؉ in comparison with positive controls representing ϳ1 to 10, 11 to 50, and >50 B pertussis organisms, respectively. In the present analysis, we compare PCR findings with those of serology, culture, positive household contact, and clinical characteristics of cough illnesses.Results. Of 392 subjects with NP specimens obtained for PCR, 376 also had NP specimens collected for culture and 282 had serum specimens. PCR and culture were positive in 86 (22%) and 23 (6%) subjects, respectively. Of the positive PCR specimens, 40 were rated 3؉, 32 were rated 2؉, and 14 were rated 1؉; 3؉ positive specimens were more prevalent among DT recipients compared with pertussis vaccine recipients. Illnesses in subjects with 3؉ positive PCR results were more typical of pertussis than were those in subjects with 2؉ and 1؉ positive results with a mean duration of cough of 48 days versus 43 and 42 days, respectively; presence of paroxysms, whoop or vomiting in 38% versus 17% and 10%, respectively; and a clinical diagnosis of definite or probable pertussis by the investigators of 26% versus 7% and 4%, respectively. Using serologic evidence of infection as the standard, sensitivity of PCR was 61%, and specificity was 88%. For 3؉ positive PCR results, the respective values were 42% and 97%.Conclusion. Our findings demonstrate that PCR is more sensitive than conventional culture for the diagnosis of pertussis. They also demonstrate a high specificity of PCR when serology with or without other confirmative criteria (culture and household contact) is used as the reference. Analysis of semiquantitative PCR results revealed that subjects with a 3؉ PCR more frequently experienced typical illness compared with patients with 1؉ or 2؉ PCR. Although specific serologic study remains a necessity in pe...

Our findings support previous epidemiological studies which noted an association between epidemic pertussis and sudden infant death syndrome. Further PCR studies with both internal and external controls should be performed.

OBJECTIVE: To compare the polymerase chain reaction (PCR) results with conventional culture results for the diagnosis of Bordetella pertussis infections. METHODS: PCR and culture were performed in the course of a large vaccine efficacy trial in Germany on specimens taken from 7153 children less-than-or-equal2 years of age with cough illness lasting >6 days, and laboratory results were compared with clinical data also obtained from the patients. Calcium alginate nasopharyngeal swabs were taken for culture and clinical data were obtained from patients. Swabs were inoculated on charcoal horse blood agar plates containing cephalexin, and then discarded. The agar plates were preincubated for 2 days at the physician's office and then shipped to the culture laboratory at the University Children's Hospital in Munich, Germany, for diagnosis of B. pertussis and B. parapertussis infections. In this laboratory, Dacron swabs for PCR were taken from each culture by a wide sweep over the culture. Swabs for PCR were stored in NaCl and sent weekly to the PCR laboratory at the University Children's Hospital in Basel, Switzerland, for PCR diagnosis of B. pertussis infections. RESULTS: B. pertussis was identified by culture in 3% (213/7153) and by PCR in 7.6% (546/7153) of the specimens. Therefore, PCR increased the identification rate of subjects with B. pertussis infection 2.6-fold. Clinical characteristics were considered according to the type of laboratory findings: group 1 consisted of 209 culture-positive and PCR-positive subjects, and group 2 of 337 culture-negative but PCR-positive subjects. Group 2 subjects were significantly more likely to have mild or atypical clinical symptoms of whooping cough than were group 1 subjects. By analyzing the PCR results of group 2 subjects semiquantitatively, it could be shown that the degree of PCR positivity correlated with the severity of the clinical symptoms of whooping cough in the patient. CONCLUSIONS: PCR identified many pertussis cases with mild or atypical clinical symptoms that were not identified by culture. Semiquantification of PCR products revealed that the less positive the PCR result, the higher was the failure rate in diagnosing pertussis by culture, and, in addition, the less typical were the clinical symptoms in the patient.