High heterogeneity in methods used for the laboratory confirmation of pertussis diagnosis among European countries, 2010: Integration of epidemiological and laboratory surveillance must include standardisation of methodologies and quality assurance

Despite extensive childhood immunisation, pertussis remains one of the world's leading causes of vaccinepreventable deaths. The current methods used for laboratory diagnosis of pertussis include bacterial culture, polymerase chain reaction (PCR) and enzymelinked immunosorbent assay (ELISA) serology. We conducted a questionnaire survey to identify variations in the laboratory methods and protocols used among participating countries included in the European surveillance network for vaccine-preventable diseases (EUVAC.NET). In February 2010, we performed the survey using a web-based questionnaire and sent it to the country experts of 25 European Union countries, and two European Economic Area (EEA) countries, Norway and Iceland. The questionnaire consisted of 37 questions which covered both general information on surveillance methods and detailed laboratory methods used. A descriptive analysis was performed. Questionnaires were answered by all 27 contacted countries. Nineteen countries had pertussis reference laboratories at the national level; their functions varied from performing diagnosis to providing technical advice for routine microbiology laboratories. Culture, PCR and serology were used in 17, 18 and 20 countries, respectively. For PCR, nine laboratories used insertion sequence IS481 as the target gene, which is present in multiple copies in the Bordetella pertussis genome and thus has a greater sensitivity over single copy targets, but has been proved not to be specific for B. pertussis. Antibodies directed against pertussis toxin (PT) are specific for B. pertussis infections. For ELISA serology, only 13 countries' laboratories used purified PT as coating antigen and 10 included World Health Organization (WHO) or Food and Drug Administration (FDA) reference sera in their tests. This present survey shows that methods used for laboratory confirmation of pertussis differ widely among European countries and that there is a great heterogeneity of the reference laboratories and functions. To evaluate the effects of different pertussis immunisation programmes in Europe, standardisation and harmonisation of the laboratory methods are needed.