A prototype model using clinical document architecture (CDA) with a Japanese local standard : designing and implementing a referral letter system.

Since clinical document architecture (CDA) became an American National Standards Institute (ANSI)-approved health level seven (HL7) Standard, many countries have begun making an effort to make local standards conform to CDA. In order to make CDA compatible with the many different local standards existing in different countries, we designed a prototype model using HL7 CDA R2 with medical markup language (MML), a Japanese medical data exchange standard. Furthermore, a referral letter system based on this model was developed. Archetypes were used to express medical concepts in a formal manner and to make 2 different standards work collaboratively. We share herein the experience gathered in designing and implementing a referral letter system based on HL7 CDA, Release 2 (CDA R2). We also outline the challenges encountered in our project and the opportunities to widen the scope of this approach to other clinical documents.