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8.7.4 OM2 - numeric observation segment

This segment contains the attributes of observations with continuous values (including those with data types of numeric, date, or time stamp). It can be applied to observation batteries of type A and C (see OM1-19-nature of test/observation).

Figure 8-8. OM2 attributes

SEQ

LEN

DT

OPT

RP/#

TBL#

ITEM#

ELEMENT NAME

1

4

NM

O



00586

Sequence Number

2

60

CE

O



00627

Units of Measure

3

10

NM

O

Y


00628

Range of Decimal Precision

4

60

CE

O



00629

Corresponding SI Units of Measure

5

60

TX

O



00630

SI Conversion Factor

6

200

CM

O



00631

Reference (Normal) Range - Ordinal & Continuous Obs

7

200

CM

O



00632

Critical Range for Ordinal & Continuous Obs

8

200

CM

O



00633

Absolute Range for Ordinal & Continuous Obs

9

200

CM

O

Y


00634

Delta Check Criteria

10

20

NM

O



00635

Minimum Meaningful Increments

8.7.4.0 OM2 field definitions

8.7.4.1 Sequence number (NM) 00586

Definition: This field contains the same value as the sequence number of the associated OM1 segment.

8.7.4.2 Units of measure (CE) 00627

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 single tests/observations (those with a nature code of A or C, as described in OM1-18-nature of test/observation) that have numeric values. This field contains their customary units of measure.

8.7.4.3 Range and decimal precision (NM) 00628

Definition: This field contains the numerically valued single observations (code A or C as described in OM1-18-nature of test/observation), specifies the total length in characters of the field needed to display the observation, and the number of digits displayed to the right of the decimal point. This is coded as a single number in the format <length>.<decimal-digits>. For example, a value of 6.2 implies 6 characters total (including the sign and decimal point) with 2 digits after the decimal point. For integer values, the period and <decimal-digits> portion may be omitted (that is, 5.0 and 5 are equivalent). More than one such mask may be transmitted (separated by repeat delimiters) when it is necessary to define multiple display formats that are possible.

8.7.4.4 Corresponding SI units of measure (CE) 00629

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 single tests/observations - the corresponding SI units of measure in the format, when these differ from the customary units of measure given in the previous field.

8.7.4.5 SI conversion factor (TX) 00630

Definition: This field contains the continuous, numerically valued tests/observations, with a nature code of A or C (see OM1-18-nature of test/observation). This is a factor for converting the customary units to SI units.

In the case that the observation units are not SI units, this field provides the formula needed to convert from the reported units to SI units, this shall include the equation needed to convert from the reporting to the SI units.

In the case that the relation is simply multiplicative, this field shall include only the conversion factor. E.g., if (results SI units) = c * (results reporting units),then only c would be stored in this field. In the case of any other functional relationship, the entire equation would be stored as a test.

8.7.4.6 Reference (normal) range for ordinal and continuous observations (CM) 00631

Definition: This field contains the reference (normal) ranges for "numeric" observations/tests with a nature code of A or C (see OM1-18-nature of test/observation). It can identify different reference (normal) ranges for different categories of patients according to age, sex, race, and other conditions.

The general format is

<ref. (normal) range1>^<sex1>^<age range1>^<age gestation1>^<species1>^<race/subspecies1>^<text condition1>~

<ref. (normal) range2>^<sex2>^<age range2>^<age gestation2>^<species2>^<race/subspecies2>^<text condition2>~

·

·

·

<ref. (normal) rangen>^<sexn>^<age rangen>^<age gestationn>^<speciesn>^<race/subspeciesn>^<text conditionn>

The components are defined in the following sections.

8.7.4.6.1 The reference (normal) range (CM)

Components: <low value & high value>

Definition: This subcomponent contains the reference (:normal) range. The format of this field is where the range is taken to be inclusive (i.e., the range includes the end points). In this specification, the units are assumed to be identical to the reporting units given in OM2-3-units of measure).

8.7.4.6.2 Sex (IS)

Definition: This subcomponent contains the sex of the patient. Refer to user-defined table 0001 - Sex for suggested values.

8.7.4.6.3 Age range (CM)

Subcomponents: <low value & high value>)

Definition: This component contains the age range (in years or fractions thereof) specified as two values separated by a subcomponent delimiter (in order to allow a simple and consistent machine interpretation of this component). Ages of less than one year should be specified as a fraction (e.g., 1 month = 0.0830, 1 week = 0.01920, 1 day = 0.0027300). However, for most purposes involving infants, the gestational age (measured in weeks) is preferred. The lower end of the range is not indicated; the upper end is, assuring that series of ranges do not overlap.

8.7.4.6.4 Gestational age range (CM)

Subcomponents: <low value & high value>

Definition: This component contains the gestational age and is relevant only when the reference range is influenced by the stage of pregnancy. A range of values is required. The gestational age is measured in weeks from conception. For example, <1&10> implies that the normals apply to gestational ages from 1 week to 4 weeks inclusive (1&4). The lower end of the range is not included; the upper end is, assuring that series of age ranges do not overlap.

8.7.4.6.5 Species (TX)

Definition: This component is assumed to be human unless otherwise stated. The species should be represented as text (e.g., rabbit, mouse, rat).

8.7.4.6.6 Race/subspecies (ST)

Definition: In the case of humans (the default), the race is specified when race influences the reference range. When normal ranges for animals are being described, this component can be used to describe subspecies or special breeds of animals.

8.7.4.6.7 Conditions (TX)

Definition: This component contains the condition as simply free text. This component allows for definition of normal ranges based on any arbitrary condition, e.g., phase of menstrual cycle or dose of a particular drug. It is provided as a way to communicate the normal ranges for special conditions. It does not allow automatic checking of these text conditions.

8.7.4.6.8 Examples

A range that applies unconditionally, such as albumin, is transmitted as:

3.0 & 5.5

A normal range that depends on sex, such as Hgb, is transmitted as:

13.5 & 18^M~
12.0 & 16^F

A normal range that depends on age, sex, and race (a concocted example) is:

10 & 13   ^M^0  &  2 ^^^B
11 & 13.5 ^M^2  & 20 ^^^B~
12 & 14.5 ^M^20 & 70 ^^^B~
13 & 16.0 ^M^70 &    ^^^B

When no value is specified for a particular component, the range given applies to all categories of that component. For example, when nothing is specified for race/species, the range should be taken as the human range without regard to race. If no age range is specified, the normal range given is assumed to apply to all ages. If the upper or lower end of a range is left out, it is assumed to be +infinity or -infinity, respectively.

When two different methods result in two different reference ranges, two different observations and corresponding OMx segments should be defined.

8.7.4.7 Critical range for ordinal and continuous observations (CM) 00632

Components: <low value ^ high value>

Definition: This field applies only to single tests/observations (i.e., a nature code of A or C, as described in OM1-19-nature of test/observations) with numeric results. When a critical range is defined for such observations, it should be recorded here in the same format as the normal range (see OM2-7-reference (normal) range-ordinal and continuous obs).

8.7.4.8 Absolute range for ordinal and continuous observations (CM) 00633

Components: <range> ^ <numeric change> ^ <%/a change> ^ <days>

Definition: This field applies only to single tests/observations with a nature code of A or C (see OM1-19-nature of test/observation). It defines the range of possible results. Results outside this range are not possible. The field should be recorded in the same format as the normal and critical ranges.

8.7.4.9 Delta check criteria (CM) 00634

Components: <low & high (CM)> ^ <numeric threshold (NM)> ^ <change (ST)> ^ <length of time-days (NM)>

Definition: This field applies to numeric tests/observations with a nature code of A or C (see OM1-18-nature of test/observation). The field describes the information that controls delta check warnings and includes four components.

1) The range to which the following applies: <low & high>.

All the ranges are defined in terms of the customary reporting units given in OM2-3-units of measure. If no value range is given, the check applies to all values.

2) The numeric threshold of the change that is detected, e.g., 10.

3) Whether the change is computed as a percent change or an absolute change. This component can have two possible values:

% Indicates a percent change

a Absolute change

4) The length of time that the service retains a value for computing delta checks. This is recorded in number of days.

More than one delta check rule can apply. 13&16^10^%^100~16.1&20^2^a^100 implies that the delta check will trigger on a 10% change when the value of the observation is between 13 and 16. The check will trigger on an absolute change of 2 when the value is between 16.1 and 20. In both cases, the system will keep the last result for 100 days. In this example, beyond 100 days, the computer will not compute a delta check because it will not have a comparison value.

8.7.4.10 Minimum meaningful increments (NM) 00635

Definition: This field contains the numerically valued single observations (a nature code of A or C, as described in OM1-19-nature of test/observation) and specifies the smallest meaningful difference between reported values (the effective resolution of the measuring instrument or technique for continuous data, or the smallest discrete interval that can occur for discrete data).

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