Comparison of PCR, Culture, and Direct Fluorescent-Antibody Testing for Detection of Bordetella pertussis

Abstract

We prospectively compared the performance of culture, direct fluorescent-antibody testing (DFA), and an in-house-developed PCR test targeting the repeated insertion sequence IS481 for the detection of Bordetella pertussis in nasopharyngeal swab specimens. We tested 319 consecutive paired specimens on which all three tests were performed. A total of 59 specimens were positive by one or more tests. Of these, 5 were positive by all three tests, 2 were positive by culture and PCR, 16 were positive by PCR and DFA, 28 were positive by PCR only, and 8 were positive by DFA only. Any specimen positive by culture was considered to be a true positive, as were specimens positive by both PCR and DFA. Specimens positive only by PCR or DFA were considered discrepant, and their status was resolved by review of patient histories. Patients with symptoms meeting the Centers for Disease Control and Prevention clinical case definition for pertussis and who had a specimen positive by PCR or DFA were considered to have true B. pertussis infections. Of the 28 patients positive by PCR only, 20 met the clinical case definition for pertussis, while 3 of the 8 patients positive by DFA only met the clinical case definition. After resolution of the status of discrepant specimens, the sensitivity, specificity, positive predictive value, and negative predictive value were 15.2, 100, 100, and 87.5%, respectively, for culture; 93.5, 97.1, 84.3, and 98.9%, respectively, for PCR; and 52.2, 98.2, 82.8, and 92.4%, respectively, for DFA. The actual positive predictive value of PCR was probably greater, as several PCR-positive patients who did not meet the clinical case definition had symptoms consistent with typical or atypical pertussis. PCR is a sensitive and specific method for the detection of B. pertussis.

Microbiologic Evaluation of Gallbladder Bile of Healthy Dogs and Dogs with Iatrogenic Hypercortisolism: A Pilot Study

“…Several studies have demonstrated that molecular methods are far more sensitive than classical culture-based methods in identifying bacterial species. 38,39 However, in a recent study on feline bile, DNA sequencing was only able to identify bacteria in 1 bile sample for which bacteria had not already been identified with bacterial cultures. f Thus, although it appears desirable to expand this study by molecular methods, the latter study suggests that positive samples may not be more frequently detected by molecular methods.…”

Response of the Clinical Microbiology Laboratory to Emerging (New) and Reemerging Infectious Diseases

“…Due to its remarkably enhanced sensitivity, PCR amplification and detection of IS481 insertion sequences in the B. pertussis genome has replaced direct fluorescent-antibody (DFA) methods and culture as the "gold standard" method for detection of this upper respiratory pathogen from nasopharyngeal secretions. A comprehensive, seminal study by Loeffelholz and colleagues (19) demonstrated that the sensitivities of conven- Fig. 1a.…”

Prevention of Infectious Diseases in Athletes

“…Diagnosis of pertussis infection is best performed through polymerase chain reaction assay (sensitivity, 94%; specificity, 97%) or through direct fluorescent antibody testing (sensitivity, 52%; specificity, 98%). Nasal swab cultures (sensitivity, 15%; specificity, 100%) are routinely performed; however, they have high false negative rates and take 7 to 12 days to yield results [33]. Physicians in the United States are legally required to report cases of pertussis to state public health departments [26].…”