The six attributes of a LOINC code are component, property, timing, system, scale and method. Interaction of property and scale attributes were covered in the April 2017 Tips to Identify the Correct LOINC Scale. We’ll explore how the LOINC Answer Lists can help.
When applying LOINC to a local code set, having supporting information at hand is key to success. In addition to a display name, it’s necessary to extract specimen information, result format type (alpha or numeric), units of measure, and methodology. Assays with numeric values will point to the mass or substance properties via units of measure: for example, mg/dL, ng/dL, g/L would all be Mass Concentration (MCNC). The LOINC scale attribute accompanying all numeric values is Quantitative (QN).
Example answers for text or alpha result fields can often be harder to locate for a computer extraction. These are often the serologies, RBC morphology, urinalysis sediment, and microbiology results. There may be a predefined answer list locally, such as P-Positive, N-Negative, E-Equivocal, or a list of organisms or “no growth” statements for microbiology. The fields could also be defined as free text, meaning anything can be typed in. Additionally, many sites use a field for canned interpretations to accompany a patient value, such as “SEE NOTE” or “SEE BELOW” in order to close out the pending work. The medical director had already approved a statement several paragraphs long, providing additional references for a clinician.
Here are the three pertinent options of the scale attribute:
ORDINAL (ORD) – ranked order of answers: Positive/Negative; Detected/Not Detected; 1+,2+,3+,4+
NOMINAL (NOM) - no relational ranking between answers: Yellow, Cloudy, Staphylococcus aureus
NARRATIVE (NAR) – multiple sentences constructed into one or more paragraphs
Now let’s talk a little more about answer choices, as they can determine if you’re allowed to use a particular LOINC term. When Regenstrief initially brought in clinical surveys, they discovered an issue dealing with copyrighted answers. Some surveys had similar questions but very different coded answers. The solution (started in release 2.61) was to create LOINC Answer terms and LOINC Lists. Wherever possible, the LOINC Answer terms are linked to SNOMED CT terms for interoperability. Use RELMA’s Answer List Search to familiarize yourself with LOINC Answers and LOINC Lists.
The RELMA tool’s comprehensive view reserves a section for possible answers and defines the LOINC List as having binding strengths of Preferred, Normative or Example. The copyrighted terms have Normative answer lists. The LOINC term may not be used for other purposes if a site’s local answers do not match the Normative list.
Here are examples of LOINC Answer Lists. Within the maternal quad screen, there are a variety of “ask at order entry” questions about the mother and her history that accompany the specimen:
- The number of fetuses being carried in a pregnancy: 55281-0 and 11878-6 are the quantitative number of Fetuses, separated by method (11878-6 is by ultrasound).
- 57722-1 Birth plurality of Pregnancy: NORMATIVE answer list 1,2,3,4-12, Unknown Plurality. The sequence numbers have a weighted ranking of 1-12, and 99 for Unknown. This LOINC may only be used when the local answer list is identical.
- 92568-5 Fetal Chorion (Type): PREFERRED answer list 0-Monochorionic; 1-Dichorionic; 2-Unknown; 3-Not applicable (not a twin pregnancy). This LOINC may be used even if the local answer list is not identical.
Race is also captured on the quad screens, and here are some examples:
- 21484-1 Mother’s race with a nominal scale: EXAMPLE answer list 1-American Indian or Alaska Native, 2-Asian, 3-Black or African American, 4-Native Hawaiian or Other Pacific Islander, 5-White, 6-Unknown. Example answer lists are meant to show possible result values; again, the LOINC may be used even if the local answer list is not the same.
- 74693-3 Race [AHRQ – Agency for Healthcare Research and Quality]: NORMATIVE answer list 1-American Indian or Alaska Native, 2-Asian, 3-Black or African American, 4-Native Hawaiian or Other Pacific Islander, 5-White, 6-More than one race, 7-Unknown. Compare this to the example above – the difference is only in the last two result values. However, this LOINC cannot be used unless you also use exactly this set of answers.
- There are at least ten Race LOINC terms, separated by copyright survey method (Office of Management and Budget OMB.1977, PhenX and US Surgeon General family health portrait - USSG-FHT, etc.)
Having de-identified sample reports pinpoints the style of scale attribute and the method of use. Get as much information as possible and make use of the answers lists to get to the right scale and LOINC term.