Identification of cases of meningococcal disease: data quality in two Danish population-based information systems during a 14-year period.

Meningococcal disease (MCD) is registered in two population-based information systems in Denmark because of the interest in long-term surveillance as a means of following trends, and in public health intervention such as chemoprophylaxis and vaccination. The two systems are the Notifiable System of Communicable Diseases (NSCD) and the Hospital Discharge Register for in-patients (HDR). The aim of the present study was to assess the data quality of the two systems over a 14-year period in the County of Northern Jutland, Denmark. All records of patients registered in the two systems were reviewed with respect to the criteria for the diagnosis of MCD. In addition, records from the local clinical microbiology department, where all microbiological examinations were carried out, were reviewed. The degree of completeness for the HDR system was 89.8% and for the NSCD system was 92.2%. In the in-patient HDR, 296 cases were registered, but only 254 cases (85.8%) fulfilled the criteria for MCD. In the notifiable system, 273 cases were registered, but only 261 cases (95.6%) fulfilled the criteria for MCD. A capture-recapture analysis showed that one to two cases apparently escaped registration.