  Introduction: A Master Patient Index(MPI) is a centralized index of all
patients in a healthcare system. This index is composed of a unique identifier
for each patient link to his/her demographic data and clinical encounters. A
MPI is essential to ensure data interoperability in the different healthcare
institution. The The health ministry of Sri Lanka planning to develop MPI for
the country. This project focused on developing the prototype MPI for Sri Lanka
with the view to implementing and scaling up at the national level. Methods:
This project consisted of 3 phases. Phase 1: requirement analysis using focus
group discussions (FGD) with information system users. Phase 2: identification
of the suitable Application Programming interface (API) model. Phase 3:
development of the prototype MPI. Results: FGD were conducted in 6 hospitals.
There were 78 interviewers (Male -36, and female - 42). They highlighted the
key requirements for the MPI. Which were the unique identification method and
different searching criteria and merging records to avoid duplication. Using
this information, the requirements specification for MPI was developed. A
combination of monolithic and microservices architecture was selected to
develop the MPI. The API using the Personal Health Number (PHN) as the unique
patient identifier and HL7 standard was developed and implemented. Conclusions:
Development and implementation of a MPI has facilitated the long due need for
interoperability among health information systems in Sri Lankan. KEYWORDS MPI,
Interoperability, Unique Identifier, PHN, API
