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Arden FAQ

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Q: What is the Arden Syntax?


Q: How do I get a copy of the Arden Syntax standard?


Q: How do I join the Arden Syntax Work Group (WG)?


Q: Which vendors of clinical information systems use the Arden Syntax in their clinical decision support applications?


Q: Which health care organizations have Arden Syntax based systems in use?


Q: Where can I get MLMs for my Arden Syntax decision support system?


Q: What implementation tools are available to help me use the Arden Syntax in my systems?


Q: What are the benefits of Arden Syntax based clinical decision support systems?


Q: Where can I read more about the Arden Syntax?


Q: Why use Arden rather than C, C++, Visual Basic, JAVA, or anything else that already exists? What are the advantages of the Arden Syntax?


Q: What are the limitations of the Arden Syntax?


Q: What does it mean when a vendor says that it is "compliant" with the Arden Syntax standard?


Q: What are the future plans for the Arden Syntax?



Q: What is the Arden Syntax?


A: The Arden Syntax specification covers the sharing of computerized health knowledge bases among personnel, information systems and institutions. The scope has been limited to those knowledge bases that can be represented as a set of discrete modules. Each module, referred to as a Medical Logic Module (MLM), contains sufficient knowledge to make a single decision. Contraindication alerts, management suggestions, data interpretations, treatment protocols, and diagnosis scores are examples of the health knowledge that can be represented using MLMs. Each MLM also contains management information to help maintain a knowledge base of MLMs and links to other sources of knowledge. Health personnel can create MLMs directly using this format, and the resulting MLMs can be used directly by an information system that conforms to this specification.


History: The Arden Syntax evolved from alerts and reminder systems at LDS Hospital in Salt Lake City (the HELP System), the Regenstrief Institute in Indianapolis (the CARE System), Columbia University Medical Center in New York (the first Arden Syntax system), and several other academic efforts. The group first met at the Arden Homestead in Harriman, NY, hence the name. The Arden Syntax was born out of the realization that the power of these alerts and reminder systems was in the knowledge, and that there was a need to make this knowledge portable, shareable, between information systems. Many commercial vendors adopted the standard and included it in their products (see below).


The first version of the Arden Syntax was administered and issued by the American Society for Testing and Materials ASTM (see below). Since 1998, the Arden Syntax group is part of the Health Level Seven International (HL7) organization, home of many widely accepted standards in health care informatics. The Arden Syntax Work Group administers the Arden Syntax standard.


Q: How do I get a copy of the Arden Syntax standard?


A: Visit the Arden Syntax product page at the HL7 International Web site.



Q: How do I join the Arden Syntax Work Group?


A: The Arden Syntax Work Group is part of the HL7 International organization. For information on HL7 meetings, contact HL7 at:


HL7 International
3300 Washtenaw Avenue
Suite 227
Ann Arbor, MI 48104-4250
phone: (734) 677-7777
fax: (734) 677-6622
email: hq@hl7.org
Web site: hl7.org


To join the HL7 Arden Syntax Work Group (ardensyntax@lists.hl7.org) or Clinical Decision Support Work Group(dss@lists.hl7.org) listservs, see instructions on the HL7 Web site.


Contact persons for information on Arden Syntax--Arden Syntax Work Group co-chairs:


Robert Jenders, MD, MS, FACP, FACMI
Center for Biomedical Informatics and Department of Medicine, Charles Drew University
Department of Medicine, University of California, Los Angeles
voice: (310) 761-4700
email: jenders@ucla.edu


Peter Haug, MD
University of Utah and Intermountain Healthcare
email: peter.haug@imail.org


Q: Which vendors of clinical information systems use the Arden Syntax in their clinical decision support applications?

A: The following vendors have applications generally available today that support the Arden Syntax:


Currently available (as of July, 2013):
Allscripts ([[1]])
McKesson ([[2]])
Medexter ([[3]])
Siemens ([[4]])


Q: Which health care organizations have Arden Syntax-based systems in use?

A: Rather than providing an exhaustive list, we list below (in alphabetical order by vendor and site) a few installed sites per vendor. Please contact the vendor directly if you need additional information. NB: As of July, 2013 this list is dated and may not be accurate.


  • Alamance Regional Medical Center, Burlington, NC (Allscripts)
  • Sarasota Memorial Hospital, Sarasota FL (Allscripts)
  • JFK Medical Center, Edison, NJ (McKesson)
  • Covenant Health, Knoxville, TN (McKesson)
  • St. Mary's Hospital, Waterbury, CT (McKesson)
  • Mississippi Baptist Health Systems, Jackson, MS (McKesson)
  • St. Vincent's Hospital, Birmingham, AL (McKesson)
  • St. Mary's Medical Center, Knoxville, TN (McKesson)
  • Chester County Hospital - West Chester, PA (Siemens)
  • McLeod Regional Medical Center, Florence, SC (Siemens)
  • Ohio State University, Columbus OH (Siemens)


Q: Where can I get MLMs for my Arden Syntax decision support system?


A: Sources listed below are available independent of your software vendor. Your software or systems vendor, if it incorporates Arden Syntax MLMs in its applications, also may supply you with a set of MLMs.



Q: What implementation tools are available to help me use the Arden Syntax in my systems?


A: Most commercial applications are developed by vendors for use primarily within their own environment. As of July, 2013, only the Medexter system offers elements that allows you to embed it into your own system.


Q: What are the benefits of Arden Syntax based clinical decision support systems?

A: Clinical alerts and reminder systems have proven to be effective in improving the quality of care and reducing the cost of care. Many publications demonstrate the effect in areas such as effective medication use, reduction of adverse drug events, infection control, preventive care and wellness, etc. See below for a list of publications documenting the effect of clinical decision support on quality and cost of care.


The Arden Syntax makes the knowledge driving such systems portable. With the Arden Syntax, hospitals and health care providers can incorporate knowledge that was developed and refined elsewhere into their systems, without the need to re-invent the wheel.


Selected bibliography of clinical decision support:


Bates DW, Cohen M, Leape LL, Overhage JM, Shabot MM, Sheridan T. Reducing the frequency of errors in medicine using information technology. J Am Med Inform Assoc 2001;8(4):299-308.

Bates DW, Gawande AA. Improving safety with information technology. N Engl J Med 2003;348(25):2526-2534.

Evans RS, Pestotnik SL, Classen DC et al. A computer-assisted management program for antibiotics and other antiinfective agents. N Engl J Med1998;338(4):232-238.

Johnston ME, Langton KB, Haynes RB, Mathieu A. Effects of computer-based clinical decision support systems on clinician performance and patient outcome. A critical appraisal of research. Ann Intern Med 1994;120:135-142.

McDonald CJ, Overhage JM, Tierney WM, Abernathy GR, Dexter PR. The promise of computerized feedback systems for diabetes care. Ann Intern Med 1996;124(1 pt 2):170-174.

Osheroff JA, Teich JM, Levick D, Saldana L, Velasco FT, Sittig DF, Rogers KM, Jenders RA. Improving Outcomes with Clinical Decision Support: An Implementer’s Guide, Second Edition. Chicago: Healthcare Information and Management Systems Society, 2012.

Pestonik SL, Classen DC, Evans RS, Burke JP. Implementing antibiotic practice guidelines through computer-assisted decision support: clinical and financial outcomes. Ann Intern Med 1996;124:884-890.

Rind DM, Safran C, Phillips RS, Wang Q, Calkins DR, Delbanco TL, Bleich HL, Slack WV. Effect of computer-based alerts on the treatment and outcomes of hospitalized patients. Arch Intern Med 1994;154:1511-1517.

Shea S, DuMouchel W, Bahamonde L. A meta-analysis of 16 randomized controlled trials to evaluate computer-based clinical reminder systems for preventive care in the ambulatory setting. J Am Med Inform Assoc 1996;3(6):399-409.

Shea S, Sideli RV, DuMouchel W, Pulver G, Arons RR, Clayton PD. Computer-generated informational messages directed to physicians: effect on length of hospital stay. J Am Med Informatics Assoc 1995;2:58-64.

Somkin CP, Hiatt RA, Hurley LB, Gruskin E, Ackerson L, Larson P. The effect of patient and provider reminders on mammography and Papanicolaou smear screening in a large health maintenance organization. Arch Intern Med 1997;157:1658-1664.

Weingarten SR, Riedinger MS, Conner L, Lee TH, Hoffman I, Johnson B, Ellrodt AG. Practice guidelines and reminders to reduce duration of hospital stay for patients with chest pain. An interventional trial. Ann Intern Med 1994;120:257-263.


Q: Where can I read more about the Arden Syntax?

A: A number of research papers have been published involving the Arden Syntax or systems that use it. See also the main bibliography.


Selected references:


Hripcsak G. Writing Arden Syntax medical logic modules. Computers in Biology and Medicine 1994;24(5):331-363.

Hripcsak G, Ludemann P, Pryor TA, Wigertz OB, Clayton PD. Rationale for the Arden Syntax. Computers and Biomedical Research 1994;27:291-324.

Jenders RA, Hripcsak G, Sideli RV, DuMouchel W, Zhang H, Cimino JJ, Johnson SB, Sherman EH, Clayton PD. Medical decision support: experience with implementing the Arden Syntax at the Columbia-Presbyterian Medical Center. Proc AMIA Symp 1995;:169-73.

Johansson B, Shahsavar N, Åhlfeldt H. Database and knowledge base integration - a query mapping method for Arden Syntax knowledge modules. Meth Inform Medicine 1996;35:302-308.

Karlsson D, Ekdahl C, Wigertz O, Shahsavar N, Gill H, Forsum U. Extended telemedical consultation using Arden Syntax based decision support, hypertext and WWW technique. Meth Inform Med 1997;36:108-114.

Samwald M, Fehre K, de Bruin J, Adlassnig KP. The Arden Syntax standard for clinical decision support: experiences and directions. J Biomed Inform. 2012 Aug;45(4):711-8.

Wigertz O, Hripcsak G, Shahsavar N, Bågenholm P, Åhlfeldt H, Gill H. Data-driven medical knowledge-based systems based on Arden Syntax. In Knowledge and decisions in health telematics. Barahona P and Christensen JP eds. Amsterdam: IOS Press, 1994;126-131.


Q: Why use Arden rather than C, C++, Visual Basic, JAVA, or anything else that already exists? What are the advantages of the Arden Syntax?


A: Arden Syntax was specifically developed for health care applications, and for embedding MLMs into clinical information systems. The following aspects make it especially suitable:


- Target user is a clinician. This is not a full-feature programming language. Arden Syntax does not include complex structures that you're used to in programming languages. MLMs are meant to be written and used by clinicians with little or no programming training.


- Explicit links to data, trigger events and messages to the target user. Arden Syntax is built to be embedded in existing clinical information systems. It clearly defines the hooks to clinical databases, and defines how an MLM can be called (evoked) from a trigger event.


- Time functions. Almost all medical knowledge somehow involves the time that something happened. Therefore, Arden Syntax defines that every data element and every event has a data/time stamp that is clinically significant. Arden Syntax includes many time functions (explicitly defined) to help users use the date and time in MLMs. Arden Syntax defines the duration of a year, a month, a week, etc., and defines how to see if certain data is less than 3 days old, if this event occurred 2 hours ago, etc. With any other language, these definitions would be dependent on the person implementing the MLM, but Arden Syntax defines them explicitly.


Q: What are the limitations of the Arden Syntax?


A: A problem that occurs with any form of clinical knowledge representation is the need to interact with a clinical database in order to provide alerts and reminders. Because database schemata, clinical vocabulary and data access methods vary widely, any encoding of clinical knowledge (such as a MLM) must be adapted to the local institution in order to use the local clinical repository. This hinders sharing of knowledge. Because Arden is the only standard for clinical knowledge representation, this problem is associated with Arden, but it is not unique to it.


Arden explicitly isolates references to the local data environment in curly braces ["{}"] in a MLM, so this is sometimes called the "curly braces problem". Efforts are underway in HL7 to help solve this problem, but it is not something that the Arden workgroup can do alone; it requires industry-wide standardization.


Another potential limitation of Arden is that it does not explicitly define notification mechanisms for alerts and reminders. Instead, this is left to local implementation and is, like database queries, contained in curly braces in a MLM. Explicit notification mechanisms in the Syntax itself may be a part of a future edition.


Q: What does it mean when a vendor says that it is "compliant" with the Arden Syntax standard?

A: Using an Arden-compliant system, a user should be able to create, import, customize or otherwise implement medical logic modules without the need for vendor or system developer intervention. Also, using such a system, a user should be able to take a MLM from another institution and alter the contents of the "{}" and make other related adjustments; the resultant MLM should compile and execute at the user's institution.


Q: What are the future plans for the Arden Syntax?


A: The Arden Syntax Work Group is working on Version 2.10, which will provide guidance on a standard data model for use with the Arden Syntax as well as incorporate the XML version of the standard in the normative section of the standard. The WG also is working on an implementation guide that will show how to use the Arden Syntax to address various challenges in delivering clinical decision support.




Prepared by: Robert A. Jenders, MD, MS (jenders@ucla.edu)


Last Updated: 23 September 2013