ASTM Subcommittee E31.15
              Health Knowledge Representation
                              
                           E 1460
      Standard Specification for Defining and Sharing
               Modular Health Knowledge Bases
                              
           Arden Syntax for Medical Logic Modules
 
 
ASTM Subcommittee E31.15, which was formed in 1990, is
concerned with "the promotion of knowledge and the
development of standards for defining and sharing health
knowledge for use on computerized systems." In 1992, the
subcommittee published E 1460, which is better known as the
Arden Syntax for Medical Logic Modules.
 
The Arden Syntax is a language for encoding medical
knowledge. Each Medical Logic Module (MLM) contains
sufficient logic to make a single medical decision. MLMs
have been used to generate clinical alerts, interpretations,
diagnoses, screening for clinical research, quality
assurance functions, and administrative support. With an
appropriate computer program (called an event monitor), MLMs
run automatically, generating advice where and when it is
needed. For example, one MLM warns physicians when a patient
develops new or worsening kidney failure.
 
Each MLM is made of slots grouped into maintenance, library,
and knowledge categories. The maintenance slots document the
title, author, institution, and validation of the MLM. The
library slots specify medically relevant comments, links to
the literature, and keywords for organizing a set of MLMs.
The knowledge slots define an MLM's behavior. They specify
the context in which the MLM is relevant, a set of criteria
to be checked, and an action to perform if the criteria are
satisfied. The syntax has provisions for querying a clinical
database and for representing time. A sample MLM is included
below.
 
The Columbia University Health Sciences Library maintains an
anonymous ftp directory and a gopher server for MLMs. The
ftp directory contains a tutorial on writing MLMs and a
collection of real MLMs donated from several sources. The
gopher server has only the MLMs.
 
 
1. To obtain MLMs via anonymous ftp:
 
     ftp cucis.cis.columbia.edu
     name: anonymous
     password: <your email address>
     cd pub/mlm
     get README
     get help.txt
     get tutorial.txt
     mget *.mlms
 
 
2. To obtain MLMs via telnet to gopher:
 
     telnet cuhsla.cpmc.columbia.edu
     login: infoseeker
     choose: "Health Sciences Resources at CPMC"
     choose: "Medical Logic Modules"
 
 
3. For questions about the Arden Syntax itself or about the
     MLM library collection, contact:
 
     George Hripcsak, M.D.
     Center for Medical Informatics
     Columbia-Presbyterian Medical Center
     161 Fort Washington Avenue, AP-1310
     New York, New York  10032
     (212) 305-5712
     hripcsa@cucis.cis.columbia.edu
 
 
4. For questions about ASTM Subcommittee E31.15, contact:
 
     T. Allan Pryor, Ph.D.
     LDS Hospital
     325 8th Avenue
     Salt Lake City, Utah  84143
     (801) 321-2128
     tapryor@cc.utah.edu
 
 
5. For questions about MLM evaluation, contact:
 
     Ove B. Wigertz, D.Sc., D.Med.
     Dept. Medical Informatics
     Linkoping University
     Linkoping, Sweden  S-58183
     (4613) 227-570, (4613) 104-131 fax
     ovewi@ami.liu.se
 
 
6. To obtain a copy of E 1460 (the Arden Syntax specification),
     and for questions about ASTM membership, contact:
 
     Terri Mecholsky
     ASTM
     1916 Race Street
     Philadelphia, PA  19103-1187
     (215) 299-5485
     (cost of the document itself is about $28)
                              
 
============================================================
                        A sample MLM
============================================================
                              
 
maintenance:
     title: Alert on low hematocrit;;
     filename: low_hematocrit;;
     version: 1.00;;
     institution: CPMC;;
     author: George Hripcsak, M.D.
          (hripcsa@cucis.columbia.edu);;
     specialist: ;;
     date: 1993-10-31;;
     validation: testing;;
 
library:
     purpose: Warn provider of new or worsening anemia.;;
     explanation: Whenever a blood count result is obtained,
          the hematocrit is checked to see whether it is
          below 30 or at least 5 points below the previous
          value.;;
     keywords: anemia; hematocrit;;
 
knowledge:
     type: data-driven;;
     data:
          blood_count_storage := event {'complete blood
          count'};
          hematocrit := read last {'hematocrit'};
          previous_hct := read last ({'hematocrit'}
              where it occurred before the time of
          hematocrit);;
     evoke: blood_count_storage;;
     logic:
          /* check that the hematocrit is a valid number */
          if hematocrit is not number then
               conclude false;
          endif;
          if hematocrit <= previous_hct-5 or hematocrit<30
          then
               conclude true;
          endif;;
     action:
          write "The patient's hematocrit ("|| hematocrit
               ||") is low or falling rapidly.";;
end: