This section last updated: 2023-09-18 (2 months ago)
For most of the measures we include separate observations for summary data, e.g., shift and 24-hour urine output totals. We also provide varying degrees of pre-coordination for the observation, the body site at which it was obtained, and the method. For example, a cardiac output based on the Fick method is distinguished from a cardiac output computed from 2D cardiac echo data.
Physiologic measures are often monitored continuously over time and the instrument reports summary “statistics” over that reporting period. For vital signs, these can include minimum, maximum, and mean value over a time period. For intake and output, the total is the summary statistic usually reported. When we address measures taken over time, we usually include 1-hour, 8-hour, 10-hour, 12-hour, and 24-hour intervals to cover the varying lengths of work shifts within and across institutions. The LOINC names of these correspond to the form of a 24-hour urine specimen. The times are recorded in the duration (third part) of the name.
The parts of clinical measurement names are largely the same as for laboratory measures, with some subtle differences that are detailed below.
For most clinical measurements, the Component is an attribute of a patient or an organ system within a patient. However, attributes of non-patient systems are also often of interest. For example, we might want to know the class of instrument used to obtain the measurement: i.e., the vendor model number or institutional inventory number of an endoscopy. Such identification numbers have a Property of ID. Infection control might want the latter reported in order to track nosocomial infections.
When attributes of an instrument or device are being reported, the System is the name of the instrument. The same is true when we report characteristics of tubes used to move fluid in and out of body cavities. For example, we might want to report the size and type of a nasogastric tube.
Table 20: Example subjects covered in clinical LOINC
|Blood pressure (systolic, diastolic, and mean)|
|Body weight (and measures used to estimate ideal body weight)|
|Cardiac output, resistance, stroke work, ejection, fraction, etc.|
|Circumference of chest, thighs, legs|
|Critical care measures|
|Emergency department case reports (CDC DEEDS)|
|Heart rate (and character of the pulse wave)|
|Intake and output|
|Major headings in operative note|
|Major headings in discharge summary|
|Major headings of history and physical|
|Obstetric ultrasound imaging|
|Pulmonary ventilator management|
|Standardized survey instruments|
|Urology ultrasound imaging|
To accommodate the special dimensions of clinical observations we have introduced new options for the kind of Property. The new kinds of Property are what you might expect from the new kinds of dimensions being measured (e.g., resistance, voltage, work per beat). However, we have also introduced three important new properties:
In clinical measures, super systems (the second subpart of the System component) may be required. For example, we distinguish head measures of a patient versus a fetus as follows:
With clinical terms we almost always have two ways of reporting. Using the first, we can report an observation by reporting a number of atomic variables which together fully describe the observation. For example, we have the following atomic observations for circumference measures. These variables let us deal with all of the unique kinds of circumferences for which we have not yet defined a pre-coordinated term. The following table shows examples of pre-coordinated names.
Table 21: Examples of Pre-Coordinated Names
|Circumference:Len:Pt:XXX:Qn||The actual measure of some circumference|
|Circumference site:Anat:Pt:*:Nom||Identifies the body part measured (specifies the System)|
|Circumference method:Type:Pt:XXX:Nom:*||Identifies the measuring technique used to obtain the circumference (answers = tape measure, derived, imaging)|
We also provide pre-coordinated terms that combine some of the atomic variables into one LOINC code. For example, we have:
8279-2 Circumference.at nipple line:Len:Pt:Chest:Qn
which provide more specificity and permit the key components of the measure to be expressed as one variable as is the convention in many clinical systems. We call these pre-coordinated codes “molecular” variables.
Within the LOINC database molecular variables will vary with respect to how many atomic components are aggregated. As is true in some laboratory areas, methods often are not included as part of a name, nor are they always reported. The most common molecular aggregation is between functional measure and a particular site of measurement (e.g., the many different intravascular sites for blood pressure measurements). But in some cases, the molecular variables represent combinations of specific measures and particular methods (e.g., the cardiac output measures). Please note that most molecular variables could also be accompanied by one or more atomic measures to provide special information about the measure, e.g., special circumstances of the measure, or the vendor model number or institutional inventory number of the measuring instrument.
When we have a variable that really reports what would have been contained in the name in a fully pre-coordinated term, we will place an asterisk in the part that will be reported as a value. For example, a variable that is used to report the anatomic site as an atomic variable, would have an asterisk (*) in the System part of the name. The variable used to report the method of a particular measure would have an asterisk (*) in the Method part of the name.
As of the December 2017 LOINC release, we have completed updating all of our radiology content according to the LOINC/RadLex Unified Model, which was developed through our collaboration with the Radiological Society of North America (RSNA).
You can find information about the unified model at the end of this document, in the LOINC/RSNA Radiology Playbook User Guide.
The following table provides a reference for how the attributes in the Unified Model correspond to the primary LOINC Parts.
Table 22: Relationship of primary LOINC Parts to Radiology attributes
|Primary Part||Radiology Attribute|
|Component 1st part (Analyte)||View, Guidance, Reason for Exam|
|Component 2nd part (Challenge)||Timing, Maneuver, Pharmaceutical|
In collaboration with North American Association of Central Cancer Registries, Inc (NAACCR, Inc), we have developed a set of LOINC codes that can be used to communicate tumor registry variables from clinical institutions to tumor registries and among tumor registries. These LOINC terms map to the content of NAACCR data set, and include variables for such things as the hospital at which the tumor was first diagnosed, the primary anatomic site of the tumor, it size, its degree of spread at the time of diagnoses, and a host of other variables of interest to the tumor registries. The NAACCR data set and other cancer-related demographics are identified by the Class TUMRRGT.
The NAACCR standards and an implementation guide for transmitting these LOINC tumor registry variables within HL7 messages are available from the NAACCR website (http://naaccr.org).