Haemophilus influenzae: the efficiency of reporting invasive disease in England and Wales.

This study compares the efficiency of a special regional survey with routine laboratory reporting to measure the incidence of invasive disease caused by Haemophilus influenzae before routine immunisation against type b strains was introduced. Incomplete reporting does not prevent the monitoring of trends, but it becomes important if the level of underreporting changes with time. This study illustrates the importance of assessing the quality of surveillance data before using them to inform policy or evaluate intervention. Underreporting to the regional survey was found to be 17% and underreporting to the Public Health Laboratory Service (PHLS) Communicable Disease Surveillance Centre (CDSC) was 24%. In response to this study a system has been set up to send reference laboratories a weekly list of reports to CDSC. Manual cross checking helps to complete the ascertainment of cases. All isolates of H. influenzae from cases of invasive disease should be sent to the reference laboratories for serotyping as well as being reported to CDSC.