Chapter 5: Standards and Interoperability

William R Hersh MD

After viewing the presentation, viewers should be able to:

Explain the importance of standards and interoperability for health and biomedical data

Discuss the major issues related to identifier standards, including the debate on patient identifiers

Describe the various message exchange standards, their explicit roles, and the type of data they exchange

Discuss the different terminology systems used in biomedicine and their origins, content, and limitations

Learning Objectives

Data standards promote consistent naming of individuals, events, diagnoses, treatments, and everything else that takes place in healthcare

Standards enhance the ability to transfer data among applications, thus leading to better system integration

Standards also facilitate interoperability among information systems and users


According to the International Standards Organization, a standard comes from “a standard document established by consensus and approved by a recognized body that provides for common and repeated use, rules, guidelines or characteristics for activities or their results, aimed at the optimum degree of order in a given context.” (ISO/IEC Guide 2 2004)


Standards facilitate an important process known as interoperability

The Institute for Electronic and Electrical Engineers (IEEE) updates its definition of interoperability regularly and its 2016 definition is “the ability of a system or product to work with other systems or products without special effort on the part of the customer. Interoperability is made possible by the implementation of standards.”


Walker 2005 has described levels of interoperability:

Level 1 – no interoperability, e.g., mail, fax, phone, etc.

Level 2 – machine-transportable (structural); information cannot be manipulated, e.g., scanned document, image, PDF

Level 3 – machine-organizable (syntactic); sender and receiver must understand vocabulary, e.g., email, files in proprietary format

Level 4 – machine-interpretable (semantic); structured messages with standardized and coded data, e.g., coded results from structured notes, lab, problem list, etc.


Interoperability Roadmap

Standards in many industries are critical, e.g., standards for railroad cars enabled different railroads to be built out around various countries, all adhering to a standard of the wheels being a certain distance apart

But there are limitations to standards, e.g., the standards for operating systems that emerged from Microsoft in the latter part of the 20th century - Microsoft Windows and Office – have benefits of widespread use but also limitations as well

Value and Limitations

The stages for the development of standards is as follows according to Hammond 2014:





Early implementation



Standards Development

Identifier standards

Transaction standards

Messaging standards

Imaging standards

Terminology standards

Types of Standards

Patient Identifiers

Benefits are easy linkage of records but can also compromise privacy and confidentiality for the patient

Reduce the problems of both duplicate and overlaid records

A duplicate record occurs when more than one record exists for a patient, whereas an overlaid record takes place when more than one patient is mapped to the same record.

Identifier Standards

Patient identifier key attributes (Connecting for Health 200%)

Unique – only one person has an identifier

Non-disclosing – discloses no personal information

Permanent – will never be re-used

Ubiquitous – everyone has one

Canonical – each person has only one

Invariable – will not change over time

Identifier Standards

Other Identifiers

The National Provider Identifier (NPI), which is assigned to all physicians in the US. The payor for Medicare in the US, the Centers for Medicare and Medicaid Services (CMS), will not process claims without use of the NPI

Employers must have a standard Employer Identifier Number (EIN). In addition, the Affordable Care Act requires health plans to have either a Health Plan Identifier (HPI) or an Other Entity Identifier (OEID) that is an identifier for use in transactions

Identifier Standards

There is a set of transaction standards for healthcare called ASC X12N

developed to encourage electronic commerce for health claims, simplifying what was previously a situation of over 400 different formats between insurance companies and others for healthcare transactions

HIPAA legislation mandated the use of the ASC X12N standards for healthcare business electronic data exchange under the guise of “administrative simplification”

Transaction Standards

The original version of ASC X12 was called 4010. This was superseded by a new version that was released in 2012 called 5010. The major transactions in 5010 and their identifier numbers include:

Health claims and equivalent encounter information (837)

Enrollment and disenrollment in a health plan (834)

Eligibility for a health plan (request 270/response 271)

Health care payment and remittance advice (835)

Health plan premium payments (820)

Health claim status (request 276/response 277)

Transaction Standards

Message exchange standards focus on different types of messages and different types of data

HL7 is the organization that develops and supports standards and is properly called HL7 International

The name HL7 comes from the OSI 7-layer model of network communications.

Messaging Standards

Version 2 of HL7 is widely used throughout health care

HL7 Version 2 is mostly a syntax. This means that the sender and the receiver must understand the meaning of the messages

Within HL7 Version 2, each message has segments, and each of the segments has a three-character identifier and then values that follow it

Messaging Standards

HL7 Version 2 message segments and identifiers:

MSH – message header

EVN – event type

PID – patient identifier

OBR – results header

OBX – result details

Messaging Standards

Example of HL7 Version 2 message:


PID|||123456^^^SMH^PI||MOUSE^MICKEY||19620114|M|||14Disney Rd^Disneyland^^^MM1 9DL

PV1|||5N|||||G123456^DR SMITH






HL7 Version 3 is an attempt to introduce semantics into messaging

HL7 Version 3 is based on Reference Information Model (RIM)

The elements of the message defined in the context of these abstract classes:

Entity – things in world, e.g., people, organizations, other living subjects, drugs, devices

Role – capability or capacity, e.g., patient, practitioner

Participation – role in context of an act, e.g., performer, target

Act – clinical or administrative definitions, e.g., observation, diagnosis, procedure

Act relationship – links between acts, e.g., diagnosis act

Messaging Standards

All clinical, administrative, financial, etc. activities of healthcare can be expressed in “constraints” to the RIM.

Messaging Standards

An example of a pulse reading in a physician’s office

Fast Health Interoperability Resources (FHIR)

With the widespread adoption of electronic health records and other clinical data systems, a new robust interoperability standard was needed.

When FHIR emerged as the leading candidate for interoperability, HL7 International took over its development.

Messaging Standards

A key component of FHIR is its Resources, which comprise the content of its messages

There are 6 types of resources: (http://www.hl7.org/fhir/resourceguide.html ):

Clinical: The content of a clinical record

Identification: Supporting entities involved in the care process

Workflow: Manage the healthcare process

Financial: Resources that support the billing and payment parts of FHIR

Conformance: Resources use to manage specification, development and testing of FHIR solutions

Infrastructure: General functionality, and resources for internal FHIR requirements

Messaging Standards

FHIR Resources

Messaging Standards

Clinical Document Architecture (CDA)

Another important activity of HL7 is the Clinical Document Architecture (CDA). CDA is important because most health care information is in the form of documents, and these are used to allow humans to read them.

The current version of CDA, Version 2, has three levels of interoperability

Level 1 – general document specification

Level 2 – adds document types with allowable structures

Level 3 – adds mark-up expressible in structured form, such as RIM

Other HL7 Standards

CDA Version 2


Document Template Types


We want to move image data from the devices that capture the data into records so that they can be viewed, and then we may want to archive them in various ways.

The Digital Imaging and Communications (DICOM) standard is intended for the transport of images.

DICOM was developed by the American College of Radiology and the National Electrical Manufacturers Association, and there is a Web site devoted to its details ( http://dicom.nema.org/ ).

Imaging Standards

DICOM Standard

Imaging Standards

The original standard for controlling and linking information from medical devices was called the Medical Information Bus (MIB). There is also an open source Integrated Clinical Environment (OpenICE, https://www.openice.info/ )

The National Council for Prescription Drug Programs’ (NCPDP, www.ncpdp.com ) SCRIPT is the communications standard between the prescriber and the pharmacy

The EHR Laboratory Interoperability and Connectivity Standard (ELINCS). ELINCS has been operationalized using HL7 Version 2.5.1. and covers the entire process of outpatient laboratory usage

Device, Prescribing, and Laboratory Standards


Over a decade ago, the need to exchange patient summaries led to the development of the Continuity of Care Record (CCR)

The goal for the CCR was to be, “a set of basic patient information consisting of the most relevant and timely facts about a patient's condition” (ASTM International 2003)

The original CCR standard, however, was not compatible with any existing standards, and this led HL7 and several vendors to create the Continuity of Care Document (CCD), which would be based on HL7 Version 3, and the Clinical Document Architecture (CDA)

Patient Summary Standards

Stage 2 of the Meaningful Use criteria set forth the required data set for patient summaries. The so-called required data set for the CCD includes:

Patient Summary Standards

Header Purpose Problems Procedures Family history Social history Payers Advance directives Alerts Medications Immunizations Medical equipment Vital signs Functional status Results Encounters Plan of care

Today’s EHRs are large, monolithic systems and not platforms on top of which other applications and innovations can be built

Mandl et al. have developed the Substitutable Medical Apps Reusable Technologies (SMART) platform, based on the idea that there should be an underlying platform upon which “apps” can built that access a common store of data and functions (Mandl 2012)

SMART has also adapted FHIR as its API for accessing data, hence the phrase SMART on FHIR. It has been implemented for EHRs and extended to areas like genomics and precision medicine applications (Mandl 2016) (Alterovitz 2015)

Messaging Standard Platforms

The benefits of computerization of clinical data depend upon its “normalization” to a consistent and reliable form so we can carry out tasks such as aggregation of patient data, clinical decision support, and clinical research

But clinical language is also inherently vague, sometimes by design, and that can be at odds with the precision of computers

Terminology standards are important for establishing reliable terms for transfer and use of data through the computer

Terminology Standards

There are a number of use cases for standardized terminology, including (Chute 2005):

Information capture – documenting findings, conditions, and outcomes

Communication – transferring information

Knowledge organization – classification of diseases, treatments, etc.

Information retrieval – accessing knowledge-based information

Decision support – implementing decision support rules

Terminology Standards

The World Health Organization (WHO) publishes the ICD classification system to collect data worldwide on the causes of morbidity and mortality

ICD is updated annually but limitations on expansion of certain categories of disease have traditionally required a major revision of ICD approximately every ten years

In the U.S., ICD is clinically modified (CM) because it is also used for reimbursement

Most of the world has used ICD-10 since 1990 and the US started ICD-10 in 2015 and ICD-9 is still in some use

International Classification of Diseases (ICD)

Although hierarchy between ICD-9-CM and ICD-10-CM is similar, the code structure is different and the number of codes in 2013 is nearly 69,000 versus approximately 14,000 in ICD-9-CM

Additionally, the US had to develop a replacement for Volume 3 of ICD-9-CM so hospital systems could report procedures on inpatients, the procedural coding system, ICD-10-PCS

ICD-10-CM provides extensive expansion and significantly more specification than ICD-9-CM (see next 2 slides)


ICD-9 vs ICD-10

ICD-10-PCS is a completely different hierarchical structure than volume 3 of ICD-9. PCS codes contain 7 alphanumeric characters and are actually built based on tables rather than on a tabular listing

It uses digits 0-9 and letters A-H, J-N, P-Z. The first character is a section (e.g. medical surgical). In the medical-surgical section: the second is the body system, the third is the root operation (standardized definitions), the fourth is the body part, the fifth is the approach, the sixth is the device and the 7th is a qualifier


There have been several informatics concerns about ICD-10-CM

One of these is the excess granularity as noted in the comparison with ICD-9

Many advocated that ICD-10 never be adopted, that it just be skipped, and the US move from ICD-9-CM directly to ICD-11

However, ICD-11 is not yet completed, and it would probably be another two, maybe three, years before the development of ICD-11-CM


DRGs were originally developed to aggregate ICD-9 codes into groups that could be used for health services research to look at hospital costs

DRG codes tend to categorize multiple different types of diseases that are in the same general body area and require the same amount of resources

All hospitalizations have been classified by their DRG, and that influences the reimbursement that hospitals receive for the hospitalization

Diagnosis Related Groups (DRGs)

RxNorm is the recommended standard for medication vocabulary for clinical drugs and drug delivery devices, developed by the National Library of Medicine (NLM)

RxNorm is the standard for e-prescribing and will support Meaningful Use

RxNorm encapsulates other drug coding systems, such as National Drug Code (NDC)

Example: 311642 (methylcellulose 10mg/ml ophthalmic solution)

Drug Terminology

DICOM was formed by the National Electrical Manufacturers Association (NEMA) and the American College of Radiology

While DICOM is a standard, vendors have modified it to suit their proprietary applications, resulting in lack of true interoperability

DICOM supports a networked environment using TCP/IP protocol (basic internet protocol) but is also applicable for offline use

Digital Imaging and Communications in Medicine (DICOM)

This is a standard for the electronic exchange of lab results transmitted to hospitals, clinics and payers

LOINC is divided into lab, clinical and HIPAA portions

The lab results portion of LOINC includes chemistry, hematology, serology, micro-biology and toxicology

The clinical portion of LOINC includes vital signs, EKGs, echocardiograms, gastro-intestinal endoscopy, hemodynamic data and others

The HIPAA portion is used for insurance claims

Logical Observations: Identifiers, Names and Codes (LOINC)

Other standards such as DICOM, SNOMED and MEDCIN have cross references (mapping) to LOINC

RELMA is a mapping assistant to assist mapping of local test codes to LOINC codes

The LOINC code for serum sodium is 2951-2; there would be another code for urine sodium

The formal LOINC name for this test is: SODIUM:SCNC:PT:SER/PLAS:QN (component:property:timing:specimen:scale)


SNOMED is the clinical terminology or medical vocabulary commonly used in software applications, including EHRs

SNOMED covers diseases, findings, procedures, drugs, etc.; a more convenient way to index and retrieve medical information

The vocabulary provides more clinical detail than ICD-9 and felt to be more appropriate for EHRs

SNOMED was required for stage 2 meaningful use to record family history, smoking history, transitions of care, hospital lab submission of reportable cases to public health agencies and submission of cancer cases to cancer registries

Systematized Nomenclature of Medicine: Clinical Terminology (SNOMED-CT)

This standard currently includes over 1,000,000 clinical descriptions

Terms are divided into 19 hierarchical categories

The standard provides more detail by being able to state condition A is due to condition B

SNOMED concepts have descriptions and concept IDs (number codes). Example: open fracture of radius (concept ID 20354001 and description ID 34227016)

Systematized Nomenclature of Medicine: Clinical Terminology (SNOMED-CT)

SNOMED links (maps) to LOINC and the International Classification of Diseases (ICD) codes

SNOMED is currently used in over 40 countries

SNOMED-CT Example: Tuberculosis

D E – 1 4 8 0 0

. . . .

. . . .

. . . Tuberculosis

. . Bacterial infections

. E = Infectious or parasitic diseases

D = disease or diagnosis

Systematized Nomenclature of Medicine: Clinical Terminology (SNOMED-CT)

The development of the Unified Medical Language System (UMLS) https://www.nlm.nih.gov/research/umls/ was launched by the NLM in the late 1980s and was an attempt to reconcile the plethora of vocabulary systems in health care

There are three components of the UMLS:

Metathesaurus – the thesaurus based on all the component vocabularies of the UMLS, described in more detail below

Semantic Network – maps generic relationships between the semantic types of the concepts that are in the Metathesaurus, such diseases and treatments

Specialist Lexicon – collection of words and terms mainly designed to assist in natural language processing applications

Unified Medical Language System (UMLS)

Standards are important for interoperability of healthcare data and information.

Identifier standards are important to identify people and organizations in healthcare

Individual patient identifiers are controversial, demonstrating value and risk to linking individuals in information systems

Messaging standards are important to move data and information between information systems

Terminology standards are important for normalizing the representation of all concepts used in health information systems