The overall organization of the survey instruments and other collections are represented in LOINC using a nested panel structure consistent with the existing model for laboratory panels. LOINC terms are created for the individual questions/items within an instrument, as well as for the panels/groups of terms representing the hierarchical nature of the instrument. We recognize that standardized assessments have psychometric properties that are essential to their interpretation, and so the data model includes elements such as the actual question text and allow answer options as attributes of the LOINC observation term.
10.2.1 Naming rules and conventions for names of collection terms (e.g. a panel, survey instrument)
LOINC creates terms for the collection as described in the section on Order Panels (batteries). Typically, the Property and Scale attributes are a hyphen (–), because the child elements (questions) vary in these axes. We create different panel terms for different versions of the same instrument where there are meaningful changes (e.g. different questions asked, different answer choices, etc). Some assessment instruments of the same version have different “forms” for various purposes that contain unique collections of items. For example, the OASIS-C has five unique forms that represent different subsets of questions that are used at various times: Start of Care, Resumption of Care, Follow-up, Transfer to a Facility, and Discharge from Agency. LOINC creates different panel terms for each of these forms.
10.2.2 Attributes of the LOINC terms for individual questions or variables
The LOINC table contains fields that store additional attributes relevant to many terms for individual questions or variables. Examples include the fields that store the exact question text, external copyright notice, example units, and the HL7 field where the content should be delivered (if Null, presume OBX).
In order to accommodate inclusion of instruments that are copyrighted by a third party, we have added an external copyright field to the LOINC Table (EXTERNAL_COPYRIGHT_NOTICE). This field stores the specified terms of use, and additionally, these terms are visually highlighted in the RELMA program when they appear in search results. We have only included content in this manner that is consistent with LOINC’s overall aim, so the content allows free use and distribution for clinical, administrative, and research purposes either with permission or under applicable terms of use.
LOINC does not usually create terms for information that has a designated field in an HL7 message. But, in order to create complete sets of items for some instruments we have created LOINC terms for items such as patient first name. To identify this content, we added an HL7 Field Sub ID to the LOINC table and indicate the corresponding HL7 place (e.g. PID-5.2).
10.2.3 Structured answer lists
The questions/items in standardized assessment instruments often have highly specialized, fixed answer lists. As described in Section 9.2, we have created a structured representation of the answer lists for the questions in assessment instruments represented in LOINC.
10.2.4 Attributes of items that vary depending on the parent collection
Some important attributes of a LOINC term for a question or variable may vary when that concept is used in different assessments or on different forms of the same assessment. For example, “measured body weight” is a variable of many different assessments. In the context of each instrument, that same concept could have different local codes, help text, validation rules, or associated branching logic. We therefore store these attributes at the level of the instance of the item in a particular panel.
10.2.5 Choosing the “display text” for a question or variable
As discussed in the previous sections, we have three fields that can capture the exact display of the question/item on the form in question. (For some instruments, it can be difficult to determine what exactly is the question text.) The Component of a LOINC term represents the thing or attribute being measured, and is the default for capturing the item text. However, there are several reasons why the Component may not be the exact item text. The most important ones include: our LOINC naming conventions do not permit certain characters (e.g. “/” or “?”) because of our internal “Part” parsing rules, that some aspects of the question are modeled in other parts of the formal LOINC name, or that there is some important aspect to the “thing being measured” (e.g. a lookback period of the last 7 days) that is not represented explicitly on the form for that particular item.
In general, for purposes of displaying the item text as it appears on the instrument, one can follow this rule:
- DISPLAY_NAME_FOR_FORM in the FORM_DATA table (RELMA) or FORMS table (CSV file export) [if populated]. This field provides an override display that is linked to the instance of the LOINC question code in a particular form. It allows for the same clinical concept to have slight presentation variances on different forms where those variances have no change in the concept meaning and accommodates instances where the LOINC naming conventions require some difference between the item and the LOINC Component. For example, an item might have the form label of “Body Mass Index (BMI)” but the LOINC Component would simply be Body mass index. We have also used the DISPLAY_NAME_FOR_FORM field in cases where minor edits in question text (e.g. referring to the subject as “patient” versus “resident”) vary by form but do not have a significant change in question meaning. If the question or variable is from a survey:
- SURVEY_QUEST_TEXT in the LOINC table [if populated]. This field is populated when the variable/item is asked as a question. In some cases, the variable has both a question and a label. In these cases, the SURVEY_QUEST_TEXT field is populated with both, in the pattern of [Label].[Question text]. For example, for item J0300 on the MDS version 3 we have “Pain Presence. Ask resident: ‘Have you had pain or hurting at any time in the last 7 days?’”
- COMPONENT in the LOINC table. This is the default display. Else:
- SHORTNAME in the LOINC table. This field contains a short display name (target is 40 characters or less).
- COMPONENT in the LOINC table. This is the default display.
In addition to these fields, some LOINC codes used in survey instruments may have other LOINC name fields such as a Long Common Name and Consumer Name. These additional names may be useful in some contexts for these items, but we will still use the above rule to capture the item’s representation in the instrument. Some of the original survey instruments modeled in LOINC may not follow this rule exactly, in part due to the fact that we did not have the full survey representation model as we do presently. Ongoing work includes reviewing where modifications may be needed.
10.2.6 Type of Method (6th part) for a question or variable
For variables linked to a defined answer list that come from an external source, it has become our policy to enter the initial source as the Method. For example, variables first entered for the Minimum Data Set (MDS) will have a Method of MDS. This does not mean that the term cannot be used in any other contexts, such as other panels or surveys. As long as the defining context of use is understood, the variable can be used in other contexts where the term is exactly the same, including the answer lists, as the original term.
10.2.7 Time Aspect (3rd part) for a question or variable
Beginning with the June 2015 LOINC release, the Time Aspect for survey questions that include a lookback period specify that lookback period as the Time rather than using Pt. This change was approved by the LOINC Clinical Committee at the February 2015 Clinical LOINC meeting and will apply to all new terms moving forward.
At the August 2015 Clinical LOINC meeting, further naming conventions were approved. These conventions include:
- Using the exact timing given in a validated survey question as the Time Aspect value (i.e., for questions with a 7-day lookback period, using 7D for Time Aspect rather than 1W)
- Adding Lifetime as a possible Time Aspect value
- For questions with a lookback range, using the longer end of the range for Time Aspect (e.g., if the question asks “In the last 2-6 months…”, the Time Aspect value will be 6Mo).
As of LOINC version 2.54, nearly all of the existing survey instrument terms that include a lookback period have an updated Time Aspect part, and we will continue to make these changes moving forward for any terms that were not updated for the 2.54 release.
10.2.8 Form Information
Assessment instruments often contain additional text either preceding or following an item to guide users in completing the form or provide additional context about the item. LOINC uses two fields, form CodingInstructions and Context, to represent this information.
When the text gives details about completing the form, for example, “Enter 88 if patient does not answer or is unable to respond”, that text is represented as form CodingInstructions.
When the text provides additional explanation or description, it is typically represented as Context. For example, along with an item recoding the number of stage 2 pressure ulcers a patient has, the form may display a clinical explanation of what a stage 2 ulcer is: “Stage 2: Partial thickness loss of dermis presenting as a shallow open ulcer with a red or pink wound bed, without slough. May also present as an intact or open/ruptured blister.” Such text is represented as Context.
These form-specific attributes are displayed on the LOINC details pages and are present in the LOINC Panels and Forms File.
10.2.9 Order/Observation/Both categorization for panel parent questions
Survey/questionnaire panel terms are represented using the same nested panel structure as laboratory panels (see the sections above), but they are not subject to the same ORDER_OBS convention. Laboratory panel parent terms are order only, since they aggregate multiple observations without carrying a standalone result value. Survey/questionnaire panel parent questions may instead be categorized as Observation or Both, since they act as groupers for follow-up subquestions rather than as laboratory orders. This allows these panel codes to be used directly as FHIR R6 observation.organizer resources without any change to LOINC itself. See Section 9.1.3 for the full ORDER_OBS categorization rules.