Evaluation of a diagnostic polymerase chain reaction assay for Neisseria meningitidis in North America and field experience during an outbreak.

CONTEXT: Meningococcal infection has a high public profile because of its dramatic presentation, high fatality rate, and propensity to occur in outbreaks and clusters of cases. Use of a diagnostic polymerase chain reaction (PCR) assay could enhance laboratory confirmation of cases and guide the public health response in North America.

OBJECTIVE

To assess the performance of a PCR assay for the diagnosis of meningococcal disease after its implementation in a North American setting and to evaluate sensitivity and specificity of the assay for the detection of prevalent bacterial isolates.

DESIGN

Laboratory evaluation of the sensitivity and specificity of a PCR assay for Neisseria meningitidis and observational study of a series of cases comparing molecular diagnosis against the criterion standard of conventional laboratory diagnostic tests.

SETTING

A Canadian province with a population of 4 million people.

PATIENTS: Children and adults presenting with suspected meningococcal disease in British Columbia.

MAIN OUTCOME MEASURES: The sensitivity and specificity of the PCR assay when compared against standard laboratory methods.

RESULTS

The PCR assay correctly identified all of 38 Canadian isolates of Neisseria meningitidis and correctly assigned the serogroup to each isolate. None of 57 other gram-positive or gram-negative bacteria or yeasts were detected by the PCR assay. In a clinical evaluation, for diagnosis of meningococcal disease, the PCR assay had a sensitivity and specificity of 91% and 76%, respectively, against conventional methods of diagnosis. Use of the PCR assay increased the laboratory confirmation of clinically suspected cases by 36%. During an outbreak, the PCR assay allowed serogroup determination in 3 of 7 cases, aiding in the public health decision to launch an immunization campaign.

CONCLUSIONS

The PCR assay is more sensitive than conventional methods for the diagnosis of meningococcal disease, and enhanced surveillance may help direct the public health response to the changing epidemiology of disease in North America.