2292. Comparison of Molecular Assays for the Diagnosis of Pertussis

BACKGROUND: Pertussis is a vaccine preventable disease caused by Bordetella pertussis with highest mortality observed in infants. Rapid diagnosis allows prompt treatment and administration of prophylaxis to those at high risk of severe disease. Molecular assays are commonly used for diagnosis because of the long turn-around time and reduced sensitivity associated with culture of samples obtained >2 weeks after symptom onset. We compared the workflow and performance of two molecular assays for the detection of B. pertussis from nasopharyngeal (NP) swab specimens. METHODS: NP swabs in universal transport media submitted to Cleveland Clinic for B. pertussis testing are routinely tested by the AmpliVue Bordetella assay (Quidel). The AmpliVue utilizes helicase-dependent amplification targeting the insertion sequence IS481 and detection in a lateral flow device. Remnant specimens (n = 112) were stored at -70° C until IRB approval was obtained for this study. The Simplexa™ Bordetella Direct PCR assay (DiaSorin Molecular) targeting IS481 for detection of B. pertussis and IS1001 for identification of Bordetella parapertussis was performed on the LIAISON MDx instrument. The Simplexa and AmpliVue results were compared. To arbitrate discordant B. pertussis results or positive results for B. parapertussis (not included in the AmpliVue assay), samples were sent to DiaSorin for sequencing. Sensitivity and specificity were determined for each assay’s detection of B. pertussis based on sequencing as the reference method for discordant samples. RESULTS: Positive results for B. pertussis were detected for 14 specimens by AmpliVue and 18 specimens by Simplexa. Discrepancy analysis by sequencing confirmed 4 B. pertussis positive specimens detected only by Simplexa and one false-positive result for each assay. The sensitivities of AmpliVue and Simplexa were 76.5% and 100%, respectively. The specificity of both assays was 98.9%. Positivity rates were 27% for 48 children ≥1 year, 4% for 25 infants, and 8% for 39 adults tested. The Simplexa B. parapertussis target detected in one child’s specimen was confirmed by sequencing. CONCLUSION: Compared with AmpliVue, the Simplexa assay required less hands on time and provided detection of more specimens containing B. pertussis. DISCLOSURES: S. S. Richter, bioMerieux: Grant Investigator, Research grant. BD Diagnostics: Grant Investigator, Research grant. Roche: Grant Investigator, Research grant. Hologic: Grant Investigator, Research grant. Diasorin: Grant Investigator, Research grant. Accelerate: Grant Investigator, Research grant. Biofire: Grant Investigator, Research grant.