The performance of mandatory and sentinel surveillance systems for communicable diseases: lessons to learn from the Italian experience

Background The surveillance of Communicable Diseases (CDs) is a keystone Public Health activity. According to the European Commission, most CDs have to be reported to the European Centre for Disease Prevention and Control. In order to gain in accurateness, sentinel surveillance systems have been established. This work is aimed at comparing the performance of the Italian mandatory and sentinel systems through two case studies: measles and hepatitis B (HBV). Methods Both measles and HBV notifications are mandatorily collected in the Italian Surveillance System for CDs; furthermore two voluntary surveillance systems are working since 2000 and 1985 respectively. Measles system relies on an average of 300 (minimum-maximum: 180–380) primary care pediatricians per year (SPES) while HBV one (SEIEVA) collects data on acute hepatitis from local health authorities covering approximately 60% of the population of the country; both systems are regarded as representative of the Italian Regions. Incidence data per 100,000 inhabitants, from 2005 to 2008, were collected from sentinel systems; on the other hand, for the mandatory one, we computed them dividing notifications by resident population reported by the National Institute of Statistics. Data were stratified by age groups: 0, 1–4; 5–9 and 10–14 for measles and 0–14, 15–24 and 25 for HBV. Results On the whole, considering the four years period, incidence data reported by SPES were 15% to over 100% higher than those obtained by the mandatory system with slight differences between age groups; interestingly, incidence data from the two systems were closer during 2008 when an outbreak took place. On the other hand, SEIEVA yielded incidence data from 26% to 12% lower than those coming from the mandatory system, except for 2008 when the overall incidence datum from SEIEVA was higher. Also the comparison of SEIEVA and the mandatory system showed some differences between age groups being the gap narrower for 25 years old. Conclusions These preliminary results suggest that sentinel surveillance systems can improve CDs monitoring and that the integration of different data sources is important to have a comprehensive view of the problem. Furthermore, personal commitment could be enhanced to achieve a better surveillance.