OBJECTIVES: In Japan, there are already some public databases (DBs) made up of real-world data (RWD), but each limits access by private enterprises or charges users a high fee. However, aggregated data from those DBs are made public, and various useful estimations may become possible by their use. In this analysis, estimation of the annual number of pneumonia patients in Japan was attempted using aggregated data from public DBs.

METHODS: Data from 3 DBs made public by the Ministry of Health, Labour and Welfare in Japan were used: (1) Patient Survey (PS), 2014; (2) Statistics of Medical Care Activities in Public Health Insurance (SMCA), 2015; and (3) Estimates of National Medical Care Expenditure(ENMCE), 2015. Data concerning the percentage of hospitalized pneumonia patients (Hosp_rate) were obtained from the PS, those concerning the treatment costs for pneumonia per patient (separate for inpatients and outpatients) (Cost_Hosp, Cost_Out) from the SMCA, and those concerning the annual total medical cost for pneumonia (AnnualCost) from the ENMCE. Using these data, the annual number of pneumonia patients (NumPat) was calculated by the following formula:

NumPat = AnnualCost/(Cost_Hosp*Hosp_rate+Cost_Out*(1-Hosp_rate))

RESULTS: The values obtained from each public DB were: Hosp_rate = 0.808, Cost_Hosp = JPY422,196($4,020), Cost_Out = JPY21,165($192), and AnnualCost = JPY338.2 billion($3.1 billion). By applying these data to the above equation, the annual number of pneumonia patients in Japan was estimated at 979,728. Instead of sensitivity analyses, we performed comparison with the number of pneumonia patients estimated from other disclosed data, and concluded that there is an acceptable level of accuracy in the estimate by the present method.

CONCLUSIONS: To our knowledge, the annual number of pneumonia patients is not reported in Japan, but it could be estimated by combining information obtained from existing public DBs. This method is considered to be applicable to other diseases.