Evaluation of estimated number of influenza patients from national sentinel surveillance using the national database of electronic medical claims.

Officially, the national official sentinel surveillance of infectious diseases (NOSSID) has been used to estimate the number of influenza patients nationwide; NOSSID is based on the Law Concerning the Prevention of Infectious Diseases and Medical Care for Patients of Infections (the Infectious Diseases Control Law). Prescription Surveillance (PS) has also provided a numerical estimate of influenza patients. This study compared these 2 estimations using NOSSID and PS with the numbers of influenza patients from all electronic medical claims (NDBEMC), which had the nearly-comprehensive data from surveys. Results showed that the estimate from NOSSID was about twice the estimate from the NDBEMC. However, the estimated number from the PS was almost equivalent to that from the NDBEMC. The estimated number of patients from NOSSID might not be precise, but NOSSID itself may be useful to monitor influenza trends.