[Evaluation of the Number of Varicella Patients Estimated by Prescription Surveillance].

OBJECT: It is important to know the precise number of varicella patients infected for evaluation of routine immunization and anti-bioterrorism attack using smallpox. Prescription Surveillance (PS) has been providing the estimated number of varicella patients up to the present. However, the estimated number of varicella patients cannot be validated because to date there has been no other comparable precise method of estimation. Recently, all electronic medical claims nationwide (NDB) have been disclosed. In this paper, we compare the number of varicella patients estimated by PS with NDB data, and adjust the number estimated with PS, if necessary.

METHOD: For both NDB and PS, we used the monthly data from April, 2010 to March, 2013. The estimation of the number of varicella patients from the PS data was adjusted by the proportion of estimated number based on PS to the one based on NDB in the entire study period. Moreover, we adjusted it month by month, if the former method may not be enough to compensate for the discrepancy between the two datasets.

RESULTS

The average discrepancy between NDB and PS was 48.00% in three years. By the adjustment using NDB in the three years, the discrepancy was improved to 11.49%. However, seasonal patterns of overestimation or underestimation were found. Conversely, by the adjustment using NDB month by month, the discrepancy was greatly reduced to 4.33%. Moreover, the seasonal patterns of overestimation or underestimation disappeared.

CONCLUSION

The number of patients based on NDB would appear the most precise number, however, there may be a delay of about one year before it becomes available. On the other hand, PS data are updated every day and provide us with the up-to-date situation. This paper found that combining the timeliness of the PS data and preciseness of the NDB data will provide substantial benefit for public health.