HL7 CDA Core Principles

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Introduction

This implementation guide specifies the Core Principles of using the Clinical Document Architecture [1].

Scope

This guide focuses on Data Types Release 1 [2]. Meanwhile an ISO specification ISO 21090 is out, also known as Data Type Release 2. The latter is subject to another im-plementation guide that will be published when ISO data types are used.

Focus of this document: HL7 Version 3 Data Types for CDA

The following chapters of this document will focus on the description of the data types and associated material. It will highlight the essentials in four chapters, all focusing on the Norwegian situation.

  • Common aspects: explains common aspects of use of CDA and XML
  • Data types: gives an overview and detailed specification of all data types used in CDA
  • Identification schemes: explains major aspects of identification and the use in CDA
  • Use of vocabulary: explains major aspects of vocabulary use in CDA.

Background

In many (European) countries, implementation guides for the use of data types in HL7 V3 are published. They take into account country specific constraints on the data types.

Legend of symbols

In this document several symbols are used.

Pfeil rechts.png This is an important item
Issue.svg This is a known open issue
Faq.svg This is a frequently asked question (FAQ) with answer
Conformance.svg This is a constraint; in some situations also the rule identification is specified, e.g. dtr1-1-ANY, which links to the corresponding validation rule.

Version history

Version Date Description Author
1.1 2019-04-24 Refurnished guide based on earlier work Kai U. Heitmann

Common aspects

Use of XML

HL7 Version 3 CDA uses the Extensible Markup Language (XML) as the exchange for-mat. It is assumed that the reader is familiar with common XML aspects. However, some constraints are made regarding the use of CDA.

Character Set

XML Example snippet
<?xml version="1.0" encoding="utf-8"?>

CDA document structure

The XML namespace for CDA Release 2 documents is urn:hl7-org:v3. This must be correctly mentioned in every XML instance. CDA XML documents starts with the root element ClinicalDocument.

XML Example snippet
<ClinicalDocument xmlns="urn:hl7-org:v3" xmlns:voc="urn:hl7-org:v3/voc"
    xmlns:xsi="http://www.w3.org/2001/XMLSchemma-instance">

    <!-- CDA Header --> 
          ...
    <!-- CDA Body -->
    <component>
        <structuredBody>
           ...
        </structuredBody>
    </component>

</ClinicalDocument>

Data types

Introduction

XML representation of data types

Exceptions using XML element content

Combined data types

Conformance information

Missing values (null flavor)

ANY as the generic data type

Boolean (BL)

Instance Identifier (II)

Encapsulated Data (ED)

Strings (ST)

Concept Descriptor (CD)

Coded with Equivalents (CE)

Coded Value (CV)

Coded Simple Value (CS)

Telecommunication Address (TEL)

Postal Address (AD)

Person Name (PN)

Organisation Name (ON)

Integer Number (INT)

Physical Quantities (PQ)

Point in Time (TS)

Intervals (IVL)

Interval of time (IVL_TS)

Interval of physical quantities (IVL_PQ)

Ratio of quantities (RTO_QTY_QTY)

Identification mechanisms

Object Identifiers (OIDs)

Instance identification

Coding scheme identification

List of identification schemes

List of code systems

Vocabulary

Code Systems

Value Sets

Appendix

  1. Clinical Document Architecture Release 2 http://www.hl7.org
  2. HL7 Data Types Release 1 http://www.hl7.org