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8.7.3 OM1 - general segment (fields that apply to most observations)

The OM1 segment contains the attributes that apply to the definition of most observations. This segment also contains the field attributes that specify what additional segments might also be defined for this observation.

Figure 8-7. OM1 attributes

SEQ

LEN

DT

OPT

RP/#

TBL#

ITEM#

ELEMENT NAME

1

4

NM

R



00586

Sequence Number

2

200

CE

R



00587

Producer's Test/Observation ID

3

12

ID

O

Y

0125

00588

Permitted Data Types

4

1

ID

R


0136

00589

Specimen Required

5

200

CE

R



00590

Producer ID

6

200

TX

O



00591

Observation Description

7

200

CE

O



00592

Other Test/Observation IDs for the Observation

8

200

ST

R

Y


00593

Other Names

9

30

ST

O



00594

Preferred Report Name for the Observation

10

8

ST

O



00595

Preferred Short Name or Mnemonic for Observation

11

200

ST

O



00596

Preferred Long Name for the Observation

12

1

ID

O


0136

00597

Orderability

13

60

CE

O

Y


00598

Identity of Instrument Used to Perform this Study

14

200

CE

O

Y


00599

Coded Representation of Method

15

1

ID

O


0136

00600

Portable

16

1

CE

O

Y


00601

Observation Producing Department/Section

17

40

XTN

O



00602

Telephone Number of Section

18

1

IS

R


0174

00603

Nature of Test/Observation

19

200

CE

O



00604

Report Subheader

20

20

ST

O



00605

Report Display Order

21

26

TS

O



00606

Date/Time Stamp for any change in Def Attri for Obs

22

26

TS

O



00607

Effective Date/Time of Change

23

20

NM

O



00608

Typical Turn-Around Time

24

20

NM

O



00609

Processing Time

25

40

ID

O

Y

0168

00610

Processing Priority

26

5

ID

O


0169

00611

Reporting Priority

27

200

CE

O

Y


00612

Outside Site(s) Where Observation may be Performed

28

1000

XAD

O



00613

Address of Outside Site(s)

29

400

XTN

O



00614

Phone Number of Outside Site

30

1

IS

O


0177

00615

Confidentiality Code

31

200

CE

O



00616

Observations Required to Interpret the Obs

32

64K

TX

O



00617

Interpretation of Observations

33

64K

CE

O



00618

Contraindications to Observations

34

200

CE

O

Y


00619

Reflex Tests/Observations

35

80

TX

O



00620

Rules that Trigger Reflex Testing

36

64K

CE

O



00621

Fixed Canned Message

37

200

TX

O



00622

Patient Preparation

38

200

CE

O



00623

Procedure Medication

39

200

TX

O



00624

Factors that may Effect the Observation

40

60

ST

O

Y


00625

Test/Observation Performance Schedule

41

64K

TX

O



00626

Description of Test Methods

42

60

CE

O


0254

00937

Kind of Quantity Observed

43

60

CE

O


0255

00938

Point Versus Interval

44

200

TX

O



00939

Challenge Information

45

200

CE

O


0258

00940

Relationship Modifier

46

200

CE

O



00941

Target Anatomic Site Of Test

47

200

CE

O


0259

00942

Modality Of Imaging Measurement

8.7.3.0 OM1 field definitions

8.7.3.1 Sequence number (NM) 00586

Definition: This field contains the first OM1 segment in a message and is described as 1, the second as 2, and so on.

8.7.3.2 Producer's test/observation ID (CE) 00587

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains the producer’s usual or preferred identification of the test or observation. Only three components should be included: <ID code>^<service text name/description>^<source list of code>. All components should be non-null. The source list may be any of those included in ASTM Tables 3 and 5, or a local code.

8.7.3.3 Permitted data types (ID) 00588

Definition: This field contains the allowed data type(s) for this observation. The codes are the same as those listed for OBX (a given observation may, under different circumstances, take on different data types). Indeed, under limited circumstances, an observation can consist of one or more fragments of different data types. When an observation may have more than one data type, e.g., coded (CE) and numeric (NM) the allowable data types should be separated by repeat delimiters. Refer to HL7 table 0125 - Value type for valid values.

8.7.3.4 Specimen required (ID) 00589

Definition: This field contains a flag indicating whether or not at least one specimen is required for the test/observation. Refer to HL7 table 0136 - Yes/no indicator as defined in Chapter 2.

Y one or more specimens are required to obtain this observation

N a specimen is not required

When a specimen is required, segment OM4 will usually be included (one per specimen is required).

8.7.3.5 Producer ID (CE) 00590

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field uniquely identifies the service producing the observation described in this segment. Three components should be included: an identifying code, the name of the producer, and the identity of the coding system (e.g., 323-5678^Acme Special Lab^MC). The identity of the coding system will usually be MC (Medicare provider number or HIBCC site codes) in the United States. Each country may want to specify its preferred coding system and define a coding system ID to identify it.

Remember that the magnitude of a treatment or the setting on a machine, such as a ventilator, can be regarded as an observation. Thus, pharmacy, respiratory care, and nursing may be producers of such observations.

8.7.3.6 Observation description (TX) 00591

Definition: This field contains a text description of this observation.

8.7.3.7 Other test/observation IDs for the observation (CE) 00592

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains all alias codes/identifiers for this observation. If more than one alias code needs to be specified, multiple three-component, CE-format entries (<code 1>^<name 1>^<code system 1>) may be given, separated by repeat delimiters. An observation may have as many names/codes as are applicable (e.g., ICD9, ACR-NEMA, SNOMED, and READ). We encourage the inclusion of as many different codes as may apply to assist cross-system mapping of terminology. All components of each triplet should be non-null (that is, names and coding system IDs within the CE data type are required in addition to codes). The source list may be any of those included in ASTM Tables 3 and 5.

Because the size (dose) of a treatment can also be an observation, codes that identify treatments (e.g., NDC, ICCS) may also be included in this field.

Note: In this field, the names within the CE data type are required.

8.7.3.8 Other names (recognized by the producer for the observation) (ST) 00593

Definition: This field contains any test aliases or synonyms for the name in the context of the ordering service. These are alternative names, not associated with a particular coding system, by which the battery, test, or observation (e.g., measurement, test, diagnostic study, treatment) is known to users of the system. Multiple names in this list are separated by repeat delimiters.

8.7.3.9 Preferred report name for the observation (ST) 00594

Definition: This field contains the preferred name for reporting the observation or battery. The name can contain up to 30 characters (including blanks). It is the preferred name for columnar reports that require a maximum name size.

8.7.3.10 Preferred short name or mnemonic for the observation (ST) 00595

Definition: This field contains the name that can be used in space-limited reports (e.g., specimen labels) to identify the observation for the convenience of human readers. The name can contain up to eight characters.

8.7.3.11 Preferred long name for the observation (ST) 00596

Definition: This field contains the fully specified name for the observation or battery. It may include the full (unabbreviated) multiple-word names and contain up to 200 characters. It should be as scientifically precise as possible.

8.7.3.12 Orderability (ID) 00597

Definition: This field indicates whether or not a test/observation is an orderable code. Refer to HL7 table 0136 - Yes/no indicator for valid values.

Y the test/observation is an orderable code

N the test/observation is not orderable

For example, blood differential count is usually an orderable "test," MCV, contained within the differential count, is usually not independently orderable.

8.7.3.13 Identity of Instrument used to perform this study (CE) 00598

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: When applicable, this field contains the instrument or device that is used to generate this observation or battery. Examples are the automated instrument in the laboratory, the imaging device and model number in radiology, and the automatic blood pressure machine on the ward. The instrument is specified as a coded entry in anticipation that these identifiers could be specified as codes. Initially, we expect that most of the information about devices will be transmitted as text in the second component of the CE identifier. If more than one kind of instrument is used, all of them can be listed, separated by repeat delimiters.

8.7.3.14 Coded representation of method (CE) 00599

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains the method(s) used to produce the observation and should be recorded in a computer-understandable (coded) form here. This field should report the same method(s) reported in narrative in the following field. More than one method may be listed, but only if they produce results that are clinically indistinguishable. Multiple methods must be separated by repeat delimiters.

8.7.3.15 Portable (ID) 00600

Definition: This field indicates whether or not a portable device may be used for the test/observation. Refer to HL7 table 0136 - Yes/no indicator for valid values.

Y the observation can be obtained with a portable device brought to the patient

N the patient or specimen must be transported to the device

8.7.3.16 Observation producing department/section (CE) 00601

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field permits the sorting of observation orders and values by the providing service’s department/section. It provides "source oriented" reporting when required. The codes for this field should be taken from ASTM Table 15 (Diagnostic Service Codes). Free text may be used instead of these codes, but in that case, they should be recorded as the second "component" of the field to distinguish them from the standard codes. Multiple codes in this field are separated by repeat delimiters.

8.7.3.17 Telephone number of section (XTN) 00602

Definition: This field contains the telephone number for calling responsible parties in this section to ask results or advice about the use of this test.

8.7.3.18 Nature of test/observation (IS) 00603

Definition: This field indicates whether the definition entry identifies a test battery, an entire functional procedure or study, a single test value (observation), multiple test batteries or functional procedures as an orderable unit (profile), or a single test value (observation) calculated from other independent observations. Refer to user-defined table 0174 - Nature of test/observation for suggested values.

User-defined Table 0174 - Nature of test/observation

Value

Description

P

Profile or battery consisting of many independent atomic observations (e.g., SMA12, electrolytes), usually done at one instrument on one specimen

F

Functional procedure that may consist of one or more interrelated measures (e.g., glucose tolerance test, creatine clearance), usually done at different times and/or on different specimens

A

Atomic test/observation (test code or treatment code)

S

Superset--a set of batteries or procedures ordered under a single code unit but processed as separate batteries (e.g., routines = CBC, UA, electrolytes)

This set indicates that the code being described is used to order multiple test/observation batteries. For example, a client who routinely orders a CBC, a differential, and a thyroxine as an outpatient profile might use a single, special code to order all three test batteries, instead of having to submit three separate order codes.

C

Single observation calculated via a rule or formula from other independent observations (e.g., Alveolar--arterial ratio, cardiac output)

Codes P, F, and S identify sets (batteries) and should be associated with an OM5 segment that defines the list of elements. The definitions for the contained elements would have to be sent in other independent OMx segments, one for each contained element. In the ASTM context, most text reports--such as discharge summaries, admission H&Ps, and chest x-ray reports--are considered as sets, in which each section of the report (e.g., description, impression, and recommendation of an x-ray report) is considered a separate observation.

Code A identifies a single direct observation and would usually be associated with an OM2 and/or OM3 segments.

Code C identifies a derived quantity and would usually be associated with an OM6 segment.

All of these codes can be associated with one or more OM4 (specimen) segments.

8.7.3.19 Report subheader (CE) 00604

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains an optional string that defines the preferred header under which this observation should be listed on a standard display. For example, if the test is hemoglobin, this string might be "Complete blood count." It is represented as a coded data type so that a battery can be a header. Only the description part of the string may be included in case the subheader does not have an associated code. When a series of observations is displayed according to the sort order given below, the subheader that groups those observations is presented whenever the subheader changes.

8.7.3.20 Report display order (ST) 00605

Definition: This field contains an optional string that defines the sort order in which this observation is presented in a standard report or display that contains the many observations.

8.7.3.21 Date/time stamp for any change in definition for the observation (TS) 00606

Definition: This field contains the date and time that the last of any field change was made and in the host’s record corresponding to the OM1 segment.

8.7.3.22 Effective date/time of change in test procedure that make results non-comparable (TS) 00607

Definition: This field contains the date and time of the last change in the test procedure that would make previous results incompatible with new results, e.g., the last time that normal reference range or units changed for a numeric test/observation.

We strongly suggest that observation producers never use the same observation ID when the measurement procedures change in such a way that results produced under the new procedure are clinically different from those produced with the old procedure. Rather, the producer should try to adjust the new procedure so that its values are clinically indistinguishable from the old. Failing that, one should create a new observation ID for the observation produced under the new procedure.

In the rare circumstances when a procedure change occurs and neither of the above two options is viable, this field shall be used to transmit the effective date-time of the new procedure. The receiving system shall assume that any values that come across under this observation ID are under the new procedure after this date and take appropriate steps to distinguish the old from the new observations.

This number is included to provide a means of communicating with the observation producing service when they have questions about particular observations or results.

8.7.3.23 Typical turn-around time from receipt of specimen/subject to result produced (NM) 00608

Definition: This field contains the typical processing time for single test/observation. This field indicates the time from the delivery of a specimen or transport of a patient to a diagnostic service and the completion of the study. It includes the usual waiting time. The units are measured in minutes.

8.7.3.24 Processing time (NM) 00609

Definition: This field contains the usual length of time (in minutes) between the start of a test process and its completion.

8.7.3.25 Processing priority (ID) 00610

Definition: This field contains one or more available priorities for performing the observation or test. This is the priority that can be placed in OBR-28-quantity/timing. For tests that require a specimen, this field may contain two components in the format <specimen priority>^<processing priority>. The first component in this case indicates the priority with which the specimen will be collected and is the priority that is specified in an OBR segment when ordering the observation. The second component indicates the corresponding priority with which the producer service will process the specimen, produce the observation, and return results, when this differs from collection priority. Refer to HL7 table 0168 - Processing priority for valid values.

Table 0168 - Processing priority

Value

Description

S

Stat (do immediately)

A

As soon as possible (a priority lower than stat)

R

Routine

P

Preoperative (to be done prior to surgery)

T

Timing critical (do as near as possible to requested time)

C

Measure continuously (e.g., arterial line blood pressure)

B

Do at bedside or portable (may be used with other codes)

The priority for obtaining the specimen is included in OM4. Multiple priorities may be given, separated by repeat delimiters. For example, S~A~R~P~T indicates that the test may be ordered using codes S, A, R, P, or T.

8.7.3.26 Reporting priority (ID) 00611

Definition: This field contains the available priorities reporting the test results when the user is asked to specify the reporting priority independent of the processing priority. Refer to HL7 table 0169 - Reporting priority for valid values.

Table 0169 - Reporting priority

Value

Description

C

Call back results

R

Rush reporting

8.7.3.27 Outside site(s) where observation may be performed (CE) 00612

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains the identification(s) of the outside service(s) that produce the observation. The format of this CE field uses the producer ID (as defined in OM1-6-producer ID) and the name of the service separated by component delimiters. An example is 39221^ACME lab^MC. If multiple services are used, they should be separated by repeat delimiter(s).

8.7.3.28 Address of outside site(s) (XAD) 00613

Components: <street address (ST)> ^ <other designation (ST)> ^ <city (ST)> ^ <state or province (ST)> ^ <zip or postal code (ST)> ^ <country (ID)> ^ <address type> (ID)> ^ <other geographic designation (ST)> ^ <country/parish code (IS)> ^ <census tract (S)>

Definition: This field contains the address of the outside services listed in OM1-28-outside site(s) where observation may be performed. If multiple services are recorded in that field, their addresses should be separated by repeat delimiters, and the addresses should appear in the same order in which the services appear in the preceding field.

8.7.3.29 Phone number of outside site (XTN) 00614

Components: [NNN] [(999)]999-9999 [X99999] [B99999] [C any text] ^ <telecommunication use code (ID)> ^ <telecommunication equipment type (ID)> ^ <email address (ST)> ^ <county code (NM)> ^ <area/city code (NM)> ^ <phone number (NM) ^ <extension (NM)> ^ <any text (ST)>

Definition: This field contains the telephone number of the outside site.

8.7.3.30 Confidentiality code (IS) 00615

Definition: This field contains the degree to which special confidentiality protection should be applied to the observation. For example, a tighter control may be applied to an HIV test than to a CBC. Refer to user-defined table 0177 - Confidentiality code for suggested values.

User-defined Table 0177 - Confidentiality code

Value

Description

V

Very restricted

R

Restricted

U

Usual control

EMP

Employee

UWM

Unwed mother

VIP

Very important person or celebrity

PSY

Psychiatric patient

AID

AIDS patient

HIV

HIV(+) patient

ETH

Alcohol/drug treatment patient

8.7.3.31 Observations required to interpret this observation (CE) 00616

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains the list of variables that the diagnostic service needs to interpret the results of an ordered study. The observations specified here should be sent to the diagnostic service as OBX segments along with the order (OBR) segment.

Example for cervical pap smear:

2000.32^date last menstrual period^AS4~2000.33^menstrual state^AS4

Example for arterial blood gas:

94700^inspired 02^AS4

These examples use AS4 codes in code/text format to identify the variables. Separate multiple items by repeat delimiters.

8.7.3.32 Interpretation of observations (TX) 00617

Definition: This field contains the clinical information about interpreting test results. Examples are the conditions (drugs) that may cause false abnormals, and the information about the sensitivity and specificity of the test for diagnoses.

8.7.3.33 Contraindications to observations (CE) 00618

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains the diagnosis or problem for which the test is a contraindication or of possible danger (e.g., pacemaker, pregnancy, diabetes). For example, if the test identified in OM1 was an intravenous pyelogram, this field would include warnings about the use of contrast media in diabetes. The contraindication diagnoses should be separated by repeat delimiters.

Most contraindication rules will be transmitted as free text. In such cases, the contents serves only as information for human reading. However, an alternative for machine readable contraindication rules also exists. The rule may be defined formally in the Arden Syntax (ASTM 1460-1992) which has syntax for defining algebraic and transcendental equations, as well as temporal and logical selection criteria based on patient information stored in the computer record. Reflex rules that are written in Arden Syntax should begin and end with a double semi-colon (;;), the Arden slot delimiter.

8.7.3.34 Reflex tests/observations (CE) 00619

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains the test names as type CE (i.e., <code>^<text name>^<coding system>) that may be ordered automatically by the diagnostic service, depending on the results obtained from the ordered battery. A screening CBC might trigger a reticulocyte count if the Hgb is less than 12. Multiple reflex tests are separated by repeat delimiters.

8.7.3.35 Rules that trigger reflex testing (TX) 00620

Definition: This field contains the rules that trigger the reflex tests listed above. If multiple reflex tests are listed in OM1-34-reflex tests/observations separated by repeat delimiters, a set of corresponding rules will be included in this section. The first rule will apply to the first test, the second to the second test, and so on.

Most reflex rules will usually be transmitted as free text. In such cases, the contents serve only as information for human reading. However, an alternative for machine readable rules also exists. The rule may be defined formally in the Arden Syntax (ASTM 1460-1992) which has syntax for defining algebraic and transcendental equations, as well as temporal and logical selection criteria based on patient information stored in the computer record. Reflex rules that are written in Arden Syntax should begin and end with a double semi-colon (;;), the Arden slot delimiter.

8.7.3.36 Fixed canned message (CE) 00621

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains the codes and a fixed text message that is always associated with an abbreviation. The field may include multiple messages separated by repeat delimiters.

Most rules about patient testing will be transmitted as free text. In such cases, the contents serves only as information for human reading. However, an alternative for machine readable rules also exists. The rule may be defined formally in the Arden Syntax (ASTM 1460-1992) which has syntax for defining algebraic and transcendental equations, as well as temporal and logical selection criteria based on patient information stored in the computer record. Rules about patient preparation are written in Arden Syntax should begin and end with a double semi-colon (;;), the Arden slot delimiter.

8.7.3.37 Patient preparation (TX) 00622

Definition: This field contains the tests or observations that require special patient preparation, diet, or medications. For GI contrast studies, this field would contain the pretest diet, e.g., low residue for two days, NPO before study, and the preferred purgatives. Each separate med, diet, or preparation should be delimited by a repeat delimiter. Separate each requirement by a repeat delimiter. Example for a sigmoidectomy: clear liquid diet full day before procedure~take 8 oz mag citrate 6pm day before procedure~take 2 ducat tabs (5m) at 4pm day before procedure~NPO past midnight.

8.7.3.38 Procedure medication (CE) 00623

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This field contains the treatments that may be needed as part of the procedure. Examples are radioactive iodine for a thyroid screen, and methacholine for a methacholine spirometry challenge. This field should be identified as a CE data type.

8.7.3.39 Factors that may effect the observation (TX) 00624

Definition: This field contains the text description of the foods, diagnoses, drugs, or other conditions that may influence the interpretation of the observation. Information about the direction of the effect, and any recommendation about altering the diet, conditions, or drug before initiating the test observation.

Most rules about factors that effect the test interpretation will be transmitted as free text. In such cases, the contents serves only as information for human reading. However, an alternative for machine readable rules also exists. The rule may be defined formally in the Arden Syntax (ASTM 1460-1992) which has syntax for defining algebraic and transcendental equations, as well as temporal and logical selection criteria based on patient information stored in the computer record. Rules about patient preparation are written in Arden Syntax and should begin and end with a double semi-colon (;;), the Arden slot delimiter.

8.7.3.40 Test/observation performance schedule (ST) 00625

Definition: This field contains the diagnostic studies/tests that are performed only at certain times during the course of a work day or work week. This field indicates the maximum interval between successive test performances (the test may actually be performed more frequently). The format given in Chapter 4, Section 4.4.2.1, "Repeat Pattern," should be used. If necessary, multiple codes may be given, separated by repeat delimiters. The use of multiple codes indicates that the test is performed at multiple concurrent intervals. For example, Q6H indicates that the test is performed at least once every 6 hours around the clock. QJ1 indicates that the test is performed at least every week on Mondays. QAM~QPM indicates that the test is performed at least once every morning and every evening. QJ1~QJ3~QJ5 indicates that the test is performed at least every week on Mondays, Wednesdays, and Fridays. C indicates that the test is performed continuously, 7 days per week.

8.7.3.41 Description of test methods (may include bibliographic citations) (TX) 00626

Definition: This field contains the text description of the methods used to perform the text and generate the observations. Bibliographic citations may be included.

8.7.3.42 Kind of quantity observed (CE) 00937

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definitions: This optional attribute describes the underlying kind of property represented by this observation. This attribute distinguishes concentrations from total amounts, molar concentrations from mass concentrations, partial pressures from colors, and so forth. These are discussed more fully in the LOINC Users’ Manual.1 They are derived from the approach described in 1995 edition of the IUPAC Silver Book. [ International Union of Pure and Applied Chemistry/International Federation of Clinical Chemistry. The Silver Book: Compendium of terminology and nomenclature of properties in clinical laboratory sciences. Oxford: Blackwell Scientific Publishers, 1995.] These distinctions are used in IUPAC and LOINC standard codes. Defined categories are listed in HL7 table 0254 - Kind of quantity.

The distinctions of true quantities in this table are based primarily on dimensional analyses. The table contains a number of "families," those related to simple counts (number, number concentration, etc.), to mass (mass, mass concentration, etc.), to enzyme activity (catalytic content, catalytic concentration, etc.), and molar or equivalents (substance content, substance concentration).

By this classification, a glucose (in the US) would be classed as a mass concentration. A sodium would be classed as a substance concentration. Within the family, a total amount should be described as the unadorned variant; e.g., the property of measure for a patient’s weight would be mass, not mass content. Most chemical measures produce concentrations, as exemplified by sodium and glucose. However, a 24-hour urine protein is not a mass concentration, but a mass rate (mass per unit time). The content variants (e.g., mass content, substance content) are used to reflect an amount per mass (usually) of tissue.

This attribute would be valued in a master file only if the service sending the master file classified observations by their principle of measurement.

Table 0254 - Kind of quantity

Enzymatic Activity

Other Properties

CACT

*Catalytic Activity

ABS

Absorbance

CNC

*Catalytic Concentration

ACT

*Activity

CCRTO

Catalytic Concentration Ratio

APER

Appearance

CCNT

*Catalytic Content

ARB

*Arbitrary

CFR

*Catalytic Fraction

AREA

Area

CRAT

*Catalytic Rate

ASPECT

Aspect

CRTO

Catalytic Ratio

CLAS

Class

Entitic

CNST

*Constant

ENT

*Entitic

COEF

*Coefficient

ENTSUB

*Entitic Substance of Amount

COLOR

Color

ENTCAT

*Entitic Catalytic Activity

CONS

Consistency

ENTNUM

*Entitic Number

DEN

Density

ENTVOL

*Entitic Volume

DEV

Device

Mass

DIFF

*Difference

MASS

*Mass

ELAS

Elasticity

MCNC

*Mass Concentration

ELPOT

Electrical Potential (Voltage)

MCRTO

*Mass Concentration Ratio

ELRAT

Electrical current (amperage)

MCNT

Mass Content

ELRES

Electrical Resistance

MFR

*Mass Fraction

ENGR

Energy

MINC

*Mass Increment

EQL

Equilibrium

MRAT

*Mass Rate

FORCE

Mechanical force

MRTO

*Mass Ratio

FREQ

Frequency

Counts

IMP

Impression/ interpretation of study

NUM

*Number

KINV

*Kinematic Viscosity

NCNC

*Number Concentration

LEN

Length

NCNT

*Number Content

LINC

*Length Increment

NFR

*Number Fraction

LIQ

*Liquifaction

NRTO

*Number Ratio

MGFLUX

Magnetic flux

Substance Amount (Moles/Millequivalents)

MORPH

Morphology

SUB

*Substance Amount

MOTIL

Motility

SCNC

*Substance Concentration

OD

Optical density

SCRTO

*Substance Concentration Ratio

OSMOL

*Osmolality

SCNT

*Substance Content

PRID

Presence/Identity/Existence

SCNTR

*Substance Content Rate

PRES

*Pressure (Partial)

SFR

*Substance Fraction

PWR

Power (wattage)

SCNCIN

*Substance Concentration Increment

RANGE

*Ranges

SRAT

*Substance Rate

RATIO

*Ratios

SRTO

*Substance Ratio

RDEN

*Relative Density

Volumes

REL

*Relative

VOL

*Volume

SATFR

*Saturation Fraction

VCNT

*Volume Content

SHAPE

Shape

VFR

*Volume Fraction

SMELL

Smell

VRAT

*Volume Rate

SUSC

*Susceptibility

VRTO

*Volume Ratio

TASTE

Taste

Miscellaneous Unit Measures

TEMP

*Temperature

ACNC

Concentration, Arbitrary Substance

TEMPDF

*Temperature Difference

RLMCNC

*Relative Mass Concentration

TEMPIN

*Temperature Increment

RLSCNC

*Relative Substance Concentration

TITR

*Dilution Factor (Titer)

THRMCNC

*Threshold Mass Concentration

TYPE

*Type

THRSCNC

*Threshold Substance Concentration

VEL

*Velocity


Time

VELRT

*Velocity Ratio

TIME

*Time (e.g. seconds)

VISC

*Viscosity

TMDF

*Time Difference



TMSTP

*Time Stamp -- Date and Time



TRTO

*Time Ratio



RCRLTM

*Reciprocal Relative Time



RLTM

*Relative Time



*Starred items are adopted from the IUPAC Silver Book,2 non-starred items are extensions.

8.7.3.43 Point versus interval (CE) 00938

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This optional attribute allows master files to classify observations as measuring the patient’s state at a point in time (e.g., spot urines, random urines, serum potassium), or averaged over a interval of time (e.g., concentration, total amount, or clearance over a 24-hour collection). Interval measures most often apply to urine and stool specimens (e.g., 24-hour urines, 3-day stool fats). They also apply to clinical measurements such as urine outputs, which are reported as shift totals and 24-hour totals, and event counts on physiologic monitors such as the number of PVCs on a 24-hour Holter monitor.

This field would only be valued in a transaction if the service sending this master file message classified its observation by point versus time interval. This field is not used to record the time collection interval for a particular sample. It is used to specify a characteristic of an observation which has a defined normal range and to distinguish observations of the same kind but observed over varying periods of time. A spot urine sodium would have PT stored in this field. A 24-hour urine sodium and a 24-hour Holter monitor would have 24H stored here. This attribute would only be valued if the filling service classified its observations by timing. Refer to user-defined table 0255 - Duration categories for suggested values.

User-defined Table 0255 - Duration categories

PT

To identify measures at a point in time. This is a synonym for "spot" or "random" as applied to urine measurements.

* (star)

Life of the "unit." Used for blood products.

30M

30 minutes

7H

7 hours

6D

6 days

1H

1 hour

8H

8 hours

1W

1 week

2H

2 hours

12H

12 hours

2W

2 weeks

2.5H

2½ hours

24H

24 hours

3W

3 weeks

3H

3 hours

2D

2 days

4W

4 weeks

4H

4 hours

3D

3 days

1L

1 months (30 days)

5H

5 hours

4D

4 days

2L

2 months

6H

6 hours

5D

5 days

3L

3 months

8.7.3.44 Challenge information (TX) 00939

Definition: This optional attribute provides information for classifying observations by the challenge component of the test, if a challenge does speciate the observation. For example, distinguishing tests that have a challenge component in database. There co-ascribes the physiologic or drug challenge that is intrinsic to the measurement. To identify, for example, tests that include a glucose challenge.

To construct this text string, use the following template. (Note: This field is not constructed of formally defined components; it is a free text field. Component delimiters are not used and it is not necessary to supply placeholders if some "components" are not used.)

The time delay follows the syntax: n<S|M|H|D|W> where n is a number (possibly a decimal); S denotes seconds; M denotes minutes; H denotes hours; D denotes days; and W denotes weeks. The time delay can be preceded by a ‘greater than’ (>) sign, e.g. >4H.

HL7 table 0256 - Time delay post challenge lists possible values for time delay.

Examples

PRE 100 GM GLUCOSE PO
PRE 100 GM GLUCOSE PO
30M POST 100 GM GLUCOSE PO
2H POST 100 GM GLUCOSE PO
TROUGH

For drug peak and trough measures the nature of the substance challenged is the same as the analyte name, and need not be included.

We denote the route of the challenge via abbreviations for medication routes (see Chapter 4, Section 4.8.3.1, "Route," HL7 table 0162 - Route of administration). An oral route of administration would be denoted by "PO," an intravenous route by "IV."

Details of the drug dose, time the dose was given, route of administration, etc., would be noted in separate OBX, and would have corresponding master observation definitions stored in the observation master file map to different records stored in the master file segments contained in the drug level message.

Table 0256 - Time delay post challenge

BS Baseline (time just before the challenge)

PEAK The time post drug dose at which the highest drug level is reached (differs by drug)

TROUGH The time post drug dose at which the lowest drug level is reached (varies with drug)

RANDOM Time from the challenge, or dose not specified. (random)

n minutes/hours/days/weeks/months/etc. after challenge begun:

1M 1 minute post challenge

2M 2 minutes post challenge

3M 3 minutes post challenge

4M 4 minutes post challenge

5M 5 minutes post challenge

6M 6 minutes post challenge

7M 7 minutes post challenge

8M 8 minutes post challenge

9M 9 minutes post challenge

10M 10 minutes post challenge

15M 15 minutes post challenge

20M 20 minutes post challenge

25M 25 minutes post challenge

20M 30 minutes post challenge

1H 1 hour post challenge

2H 2 hours post challenge

2.5H 2 1/2 hours post challenge

3H 3 hours post challenge

4H 4 hours post challenge

5H 5 hours post challenge

6H 6 hours post challenge

7H 7 hours post challenge

8H 8 hours post challenge

8H SHIFT 8 hours aligned on nursing shifts

12H 12 hours post challenge

24H 24 hours post challenge

2D 2 days

3D 3 days

4D 4 days

5D 5 days

6D 6 days

7D 7 days

1W 1 week

10D 10 days

2W 2 weeks

3W 3 weeks

4W 4 weeks

1L 1 month (30 days) post challenge

2L 2 months (60 days) post challenge

3L 3 months (90 days) post challenge

The nature of a physiologic (non-drug) challenge may also be specified, using the terms in HL7 table 0257 - Nature of challenge.

Table 0257 - Nature of challenge

Value

Description

CFST

Fasting (no calorie intake) for the period specified in the time component of the term, e.g., 1H POST CFST

EXCZ

Exercise undertaken as challenge (can be quantified)

FFST

No fluid intake for the period specified in the time component of the term

8.7.3.45 Relation modifier (CE) 00940

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This optional attribute provides a mechanism for classifying observations according to the subject, in relation to the patient whose results might be stored with as "patient" data. It is standard practice, for example, to report values for controls, donors, and blood product units as well as the patient’s own values, and store them in the patient’s record. (This may not be the best way to model such information, but it is the way it is usually reported.) This should be valued when two values (e.g., one for patient and one for a blood product unit) could otherwise be confused.

The default value is "Patient," and if not specified, this value is assumed. The persons sub-component can refer to HL7 table 0258 - Relationship modifier for valid values.

Table 0258 - Relationship modifier

Value

Description

CONTROL

Control

PATIENT

Patient

DONOR

Donor

BPU

Blood product unit

8.7.3.46 Target anatomic site of test (CE) 00941

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This optional attribute formally indicates the site of the observation (to make it easy for a system to find all tests related to one anatomic site). It can be used to classify the observation by target site of the examination. For example, "heart" might be recorded as the target of the electrocardiogram, cardiac echo, and thallium exercise test. This attribute would be applicable to most imaging and electro-physiologic examinations. The SNOMED topology axis is an example of a coding system for anatomic sites. User-defined tables may also apply here.

8.7.3.47 Modality of imaging measurement (CE) 00942

Components: <identifier (ST)> ^ <text (ST)> ^ <name of coding system (ST)> ^ <alternate identifier (ST)> ^ <alternate text (ST)> ^ <name of alternate coding system (ST)>

Definition: This optional attribute describes the modality used to classify the observations, e.g., radiograph, ultrasound, CT scan, NMR, etc.. This attribute is especially important for imaging studies. Refer to user-defined table 0259 - Modality for suggested values; it is adopted from DICOM C.7.3.1.1.1 Modality. If these are used, the code source ID would be DCM.

User-defined Table 0259 - Modality

Value

Description

Value

Description

AS

Angioscopy

FS

Fundoscopy

BS

Biomagnetic Imaging

LP

Laparoscopy

CD

Color Flow Doppler

LS

Laser Surface Scan

CP

Colposcopy

MA

Magnetic Resonance Angiography

CR

Computed Radiography

MS

Magnetic Resonance Spectroscopy

CS

Cystoscopy

NM

Nuclear Medicine (radioisotope study)

CT

Computed Tomography

OT

Other

DD

Duplex Doppler

PT

Positron Emission Tomography (PET)

DG

Diapanography

RF

Radio Fluoroscopy

DM

Digital Microscopy

ST

Single Photon Emission Computed Tomography (SPECT)

EC

Echocardiography

TG

Thermography

ES

Endoscopy

US

Ultrasound

FA

Fluorescein Angiography

XA

X-Ray Angiography

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