###### Abstract  
Collecting patient's medical data is essential for emergency care. Although hospital-tethered personal health records (PHRs) can provide accurate data, they are not available as electronic information when the hospital does not develop and supply PHRs. The objective of this research was to evaluate whether a mobile app can assemble health data from different hospitals and enable interoperability. Moreover, we identified numerous barriers to overcome for putting health data into one place. The new mobile PHR (mPHR) application was developed and evaluated according to the four phases of the system development life cycle: defining input data and functions, developing a prototype, developing a mobile application, and implementation testing. We successfully introduced the FirstER (First for Emergency Room) platform on 23 September 2019. Additionally, validation in three tertiary hospitals has been carried out since the launch date. From 14 October to 29 November 2019, 1051 cases registered with the FirstER, and the total download count was 15,951 records. We developed and successfully implemented the mPHR service, which can be used as a health information exchange tool in emergency care, by integrating medical records from three different tertiary hospitals. By recognizing the significance and limitations of this service, it is necessary to study the development and implementation of mPHR services that are more suitable for emergency care. emergency medicine; interoperability; mobile applications; personal health records; electronic medical records +
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an emergency department (ED) that they regularly visit, physicians can obtain medical information without any additional effort [3]. In South Korea, medical records are transferred by paper or telephone when patients decide to move from one hospital to the other. Meanwhile, in the case of an unexpected visit to a nearby hospital, especially in an emergency, it is hard to know a patient's detailed history because patients do not remember exactly their prior illnesses, doses, or types of drugs taken [4]. Although hospital-tethered personal health records (PHRs) can provide accurate data, they are not available as electronic information when the hospital does not develop and supply PHRs [5]. Although the need for convenient access to medical information has been increasing, several factors have limited the development of a PHR platform: related laws, ownership of data, privacy, and security [6]. The patient Privacy Act states that electronic medical records (EMRs) must not be leaked or stored outside of hospitals [7]. However, on account of the high penetration rate of EMRs and the elevated usage rate of smartphones in the country, there has been sufficient social consensus for developing PHRs [8]. Meanwhile, established policies and systems for collecting and utilizing individual medical records have been implemented that have enabled the storage of EMR data in cloud systems outside the boundaries of hospitals. Additionally, operable PHR apps have become available that tether EMRs and link several hospitals [9]. In this context, the Korean government announced a voluntary program called \"MyData\" in 2019, which gives consumers increased access to their data in portable electronic devices, such as smartphones. This program is a paradigm shift of personal data storage and management that propels the current institution-centric system to a person-centric system, which has already been adopted in medical fields in numerous countries [10]. The MyData program has been applied to various fields, including the health industry, and enables individuals to manage their own health data more actively and efficiently. The development of a new PHR application for emergencies was carried out as the medical part of this program.