Saturday, May 12, 2007

Knowledge, Standards, and the Healthcare Crisis: Part 2

In my previous post, I discussed how knowledge is the foundation of healthcare improvement, and how health information exchange is vital for creating and using knowledge. I then introduced the notion that standards are essential for sharing information and implementing knowledge in a way that improves patient care. I also mentioned that, while beneficial, there are substantial challenges to the effective implementation of standards.

Continuing on the topic of Knowledge, Standards and the Healthcare Crisis, I will now begin define what standards actually are.

What are standards?

Standards are models, principles, policies, or rules that provide an agreed-upon framework for doing and understanding things. There are many different types of standards. When it comes to health information exchange, both data and technology standards are important. These standards describe (a) how health data are to be categorized and defined and (b) how different software systems are to communicate with each other when exchanging data. I will now discuss each.

Data standards

Data standards can be divided into at least four categories: terminology, measurement, care process, and messaging format standards. In this post, I describe terminology standards.

Terminology Standards Defined

Health-related terminologies are sets of terms representing a system of concepts within a specified field (domain) of healthcare. In other words, a terminology standard refers to a "nomenclature," i.e., a systemic way of naming and categorizing things in a given category.

Terminology standards include classifications and vocabularies that group together related terms so they can be more easily and consistently understood. Classifications arrange related terms for easy retrieval. Vocabularies use sets of specialized terms to facilitate communication by reducing ambiguity.

Take, for example, the term "high blood pressure" -- the following terms are synonyms of high blood pressure or the names of conditions referring to it:

accelerated hypertension; arteriolar nephrosclerosis; benign hypertension; benign intracranial hypertension; chronic hypertension; essential hypertension; familial hypertension; familial primary pulmonary hypertension; genetic hypertension; hypertension-essential; hypertension-malignant; hypertension-renovascular; hypertensive crisis; idiopathic hypertension; idiopathic pulmonary hypertension; malignant hypertension; nephrosclerosis-arteriolar; pph; pregnancy-induced hypertension; primary obliterative pulmonary vascular disease; primary pulmonary hypertension; primary pulmonary hypertension (pph); primary pulmonary vascular disease; pulmonary arterial hypertension, secondary; pulmonary hypertension; renal hypertension; secondary pulmonary hypertension; severe hypertension; toxemia; toxemia of pregnancy[1], hyperpiesia, and hyperpiesis.

Now imagine two electronic health record systems attempting to exchange patient data. One system is able to recognize the term "high blood pressure" and the other the term "hypertension," but neither can recognize both terms. These two computers would be unable to share the data because they don't "understand" what each other is "saying." This is because computers cannot deal with synonyms (using different words to say the same thing) or homonyms (when the same terms or phrase means different things in different contexts). So, when multiple healthcare providers treat the same patient (who may have multiple health problems), exchanging patient data can be difficult, which is due to the issues of semantics and syntax.

Semantics and Syntax

Semantics and syntax are standards of language. Semantics refers to the meaning of words, expressions and sentences, i.e., how they are defined. Syntax, on the other hand, is the structural or grammatical rules that define how symbols in a language may be combined to form words, phrases, expressions, etc., which includes spelling and word order. For example, in the U.S., this pattern of numbers "###-##-####" could be the syntax for coding a Social Security Number and mmm/dd/yyyy the syntax for a date.

In the situation above, there is semantic confusion since the two software systems define excessive blood pressure using different terms (high blood pressure vs. hypertension). Syntax would be a problem if, for example, both systems used the term high blood pressure, but only one required that the three words be connected, i.e., "high_blood_pressure".

Classifications and vocabulary terminology standards attempt to address these issues.


Terminology classification standards in healthcare use a hierarchical index. The ICD-9 diagnostic standards, for example, classifies high blood pressure using this hierarchical index: Diseases of the circulatory system > Hypertensive disease > Essential hypertension (which includes high blood pressure; hyperpiesia; hyperpiesis; arterial, essential, primary and systemic hypertension; and hypertensive vascular); and it gives it a classification code number of 401.[Update; The ICD-10 is not being used]


Terminology vocabularies standards, on the other hand, often consist of "controlled vocabularies," which are similar to the Library of Congress Subject Headings used by most libraries cataloguing books. Another example is the Yellow Pages in the phone book where, for example, car dealerships are listed under "Automobiles" instead of "Cars" or "Dealerships." Automobiles is, therefore, the "controlled vocabulary" used by the yellow pages.

In healthcare, the MeSH thesaurus is a controlled vocabulary catalog for searching biomedical and health-related information and documents. Searching for "high blood pressure" in the MeSH database returns the heading "Hypertension" and defines it as "Persistently high systemic arterial BLOOD PRESSURE. Based on multiple readings (BLOOD PRESSURE DETERMINATION), hypertension is currently defined as when SYSTOLIC PRESSURE is consistently greater than 140 mm Hg or when DIASTOLIC PRESSURE is consistently 90 mm Hg or more." So, MeSH says "hypertension" should be the term everyone uses to define blood pressure readings within this range; and if they use a different term, it should be translated to "hypertension."

Examples of Existing Terminology Standards

Following are some of the healthcare terminology standards system in use today:
  • International Classification of Diseases (ICD) codes for diagnosis disorders
  • International Classification of Impairments, Disabilities and Handicaps (ICIDH) codes for diagnosis handicaps
  • International Classification of Nursing Practice (ICNP) for class nursing vocabularies
  • Diagnostic and Statistical Manual (DSM) codes for classification of mental disorders
  • Logical Observations: Identifiers, Names, and Codes (LOINC) codes for representing laboratory tests and procedures
  • Current Procedural Terminology (CPT) codes for identifying conventional treatment procedures
  • Advanced Billing Concept (ABC) codes for identifying integrative medicine procedures
  • Digital Imaging and Communications in Medicine (DICOM) for distributing and viewing any kind of medical image
  • Health Care Financing Association (HCFA) that controls Medicare and Medicaid and supports standards for reimbursement
  • Unified Medical Language System (UMLS), a system linking together various medical vocabularies
  • Systematized Nomenclature of Medicine-Clinical Terms (SNOMED-CT), a system of standardized medical terminology
  • The Medical Subject Headings (MeSH) thesaurus, a controlled vocabulary produced by the National Library of Medicine and used for indexing, cataloging, and searching for biomedical and health-related information and documents
  • Health Plan Employer Data and Information Set (HEDIS) is a standardized set of 60 performance measures for managed care plans.
In my next post, I define measurement, care process and messaging standards.


[1] ICON Health Publications Official Health Sourcebooks