Haemophilus influenzae is a common cause of respiratory tract infections. Most strains of H. influenzae are opportunistic pathogens and rarely cause invasive disease unless other factors concur (i.e. viral infections, immunological deficits). Nevertheless, invasive bacterial diseases account for severe clinical features and child mortality. Therefore, surveillance of H. influenzae is of the utmost importance. An integrated surveillance for this pathogen entails epidemiological as well as laboratory surveillance. ECDC promotes the performance of External Quality Assurance (EQA) schemes, in which laboratories are sent simulated clinical specimens or bacterial isolates for testing by routine and/or reference laboratory methods. EQA schemes or proficiency laboratory testing provides information about the accuracy of different characterisation and typing methods as well as antimicrobial susceptibility testing, and the sensitivity of the methods in place to detect a certain pathogen or novel resistance patterns. In January 2009 a collection of six strains of Haemophilus spp. (two non-capsulated H. influenzae, one H influenzae serotype a−, one H. influenzae serotype b−, one H influenzae serotype e, one H parahaemolyticus) and one other microorganism (Aggregatibacter aphrophilus, which could be misidentified as Haemophilus spp.) was sent to 26 participating reference laboratories in the IBD-Labnet surveillance network for quality assurance testing. The laboratories were requested to perform standard laboratory protocols for the methods usually used by the laboratory for: species identification, biotyping and serotyping by serological methods and/or PCR. Antimicrobial susceptibility tests and beta-lactamase testing were also requested for those laboratories that perform antimicrobial susceptibility testing of the isolates on a routine basis. The EQA performance has shown that European Haemophilus Reference Laboratories differ in the level of characterisation of the strains, ranging from simple speciation to full identification and typing. Similarly, some laboratories routinely serotype isolates whereas others do not. Some laboratories (not all) perform PCR-based capsular genotyping; some laboratories routinely perform antimicrobial susceptibility testing whilst others do not. The EQA scheme identified some problems with the use of slide agglutination for serotyping. The results can be misinterpreted when non-specific agglutination, cross-reactions and auto-agglutination occur. The results of this EQA exercise suggest that some laboratories that do perform PCR-based capsular typing only use b primers and do not test for other capsular types. The antimicrobial susceptibility testing proved difficult to interpret since, in many cases, the methodology and breakpoints used were not defined. Some laboratories used MIC values, whereas others gave zone sizes, with or without interpretation of the results. The reporting of the results by the laboratories was also heterogeneous: some submitted the results electronically, others by fax. This EQA scheme has pointed out that it should be advisable to use PCR-based genotyping methods to genotype/serotype strains giving inconclusive results on slide agglutination. This is of particular importance when routine Hib immunisation is used in order to detect Hib vaccine failures. In addition, molecular capsular typing can act as a quality control measure to monitor the accuracy of the results of conventional serotyping. In the future, it would also be appropriate the use of an electronic form completed online for reporting the results. In conclusion, the results of the EQA distribution for Haemophilus influenzae were excellent and compared favourably with the results from the EQA distribution that took place in 2007 under the auspices of EU-IBIS.
