Tim Benson
The NHS Connecting for Health programme has recently resolved to use HL7 CDA (Clinical Document Architecture) for future clinical messages. The central idea of CDA is that each message includes a human readable representation of its content, which has persistence and can be authenticated, and may also contain structured clinical data, defined using the HL7 V3 clinical statement model.
Why is this a step forward? Let’s go back to basics. Computers serve two core functions: communication and counting. Communication is a fundamental healthcare activity. Billions of clinical documents are produced every year in the NHS. One of the reasons why hospitals exist is to facilitate quick person-to-person communication (verbal and written).
It is useful to distinguish four levels of healthcare communication:
- From the healthcare provider to purchasers and other agencies;
- Between different healthcare providers (hospitals, GPs and community);
- Between clinicians and specialist departments, to request services and to report results;
- Within the immediate clinical work-group responsible for the care of individual patients (doctors, nurses and others).
These levels are listed in increasing order of volume and clinical need, but paradoxically, in decreasing order of IT investment. One reason for this paradox is that most computers are procured by managers, and managers need data that can be counted – the second basic function of computers. Most management, analysis and research is based on counting.
If you want managers’ support, the computer system has to help the bean counters. If you want clinicians’ support, the information system has to help clinicians communicate efficiently and effectively. CDA provides a way of supporting both requirements.
Any patient record, whether paper-based or electronic, is essentially a collection of documents related to an individual patient. Well-formed documents have a clearly identified originator, a list of recipients and a clear context. If there is any doubt about how to interpret a message, the receiver can contact the author and request elaboration.
Contrast this view with that of a traditional EDI (electronic data interchange) message, where the recipient, or a later user, may not know who was responsible for the original data. Lack of contextual information can make it difficult to judge the reliability of information and creates risks to patient safety.
The innovative aspect of CDA is that all CDA documents can be rendered in a human-readable way for viewing using a browser, while coded and other structured data can also be included to enable clinical decision support, audit and analysis. Furthermore. the barrier to entry is low. Relatively simple systems can process CDA documents by simply rendering the narrative text, while more sophisticated systems can work with richer computer-processable content. This provides a straight-forward migration path towards new functionality.
CDA provides a standard structure for exchanging data in a way that supports person-to-person communication alongside structured countable data. NHS CFH is adopting the new CDA Release 2 standard, which became an ANSI-approved HL7 standard in May 2005.
References and Further Information:
Dolin RH et al. HL7 Clinical Document Architecture, Release 2. J Am Med Inform Assoc. 2006;13:30-39.
Dolin RH et al. HL7 Clinical Document Architecture, Release 2. ANSI-approved HL7 Standard, May 2005. Ann Arbor, MI:Health Level Seven, Inc., 2005.
The HL7 UK 2006 Conference in London on 25-26 October includes a special pre-conference tutorial on CDA on 24 October 2006. See www.abies.co.uk.