The Impact of Switching International Classification of Diseases Version on the Surveillance System: Influenza-Like Illness Cases from The Real-Time Outbreak and Disease Surveillance System

DOI: 10.6525/TEB.20170919.33(18).002

Chia Wei, Yu-Lun Liu, Hung-Wei Kuo, Hao-Yuan Cheng, Ding-Ping Liu

2017 Vol.33 NO.18

Correspondence Author: Chia Wei

  • Epidemic Intelligence Center, Centers for Disease Control, Ministry of Health and Welfare, Taiwan


The World Health Organization (WHO) announced that there will be no new code updates on The International Statistical Classification of Diseases and Related Problems, 9th version (ICD-9) after October 2014. As the result, Taiwan starts using ICD-10-CM as the replacement for ICD-9-CM on 2016. The aim of this study is to determine the impact of switching ICD version on the surveillance system by analyzing the ICD codes reported from the hospitals. The influenza-like illness (ILI) cases reported to the Real-time Outbreak and Disease Surveillance System (RODS) is selected as an example in this study. The RODS is one of the surveillance systems in Taiwan, which collects data from emergency room visits.

All the ILI reported from 2013 to 2016 in ICD-9-CM codes from RODS were examined. In these four years, several hospitals were found to report in invalid ICD-9-CM codes, which resulted in 3.7% of the cases not classified into ILI. The other issue was that the ICD-9-CM and ICD-10-CM codes were not always in one-to-one mapping, especially when one ICD-10-CM code could be mapped to multiple ICD-9-CM codes since the system converts to the ICD-10-CM according to the sequential order of ICD-9-CM numbering system. The results of our study showed the impact of switching ICD version on the trend of ILI ER visits is minimum; however, the trend would be affected if both codes are not one-to-one mapping.

The results of this study will be applied to other surveillance systems which are also using ICD codes to enhance surveillance quality in Taiwan. In addition, the findings can serve as a basis for future research and hospital internal training regarding ICD coding system.