LOINC Codes | Medplum

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LOINC (Logical Observation Identifiers Names and Codes) was established with the intention of defining a universal standard for identifying clinical data in electronic reports. The overall scope of LOINC is anything you can test, measure, or observe about a patient.

This guide aims to provide a basic understanding of LOINC codes and how they are applied in practice.

Adopting LOINC codes for clinical data helps:

• Leverage clinical best practices for recording patient data
• Streamline CLIA/CAP and ONC certification
• Simplify billing for diagnostics

LOINC codes are most often used on Observation and ObservationDefinition resources to indicate the quantity being measured, and the US core guidelines require LOINC codes to be used for their representation of patient vitals.

You can learn more about LOINC codes by reading their getting started guide, and you can search for relevant codes using the LOINC online browser.

Types of LOINC Codes

At the highest level, there are two major divisions of LOINC codes: Laboratory and Clinical

Laboratory

Laboratory codes represent anything that you can measure or observe about a specimen extracted from a patient. It contains the usual categories of chemistry, hematology, serology, microbiology, toxicology; as well as categories for cell counts, antibiotic susceptibilities, and more

Examples

Clinical Codes

Clinical codes represent "everything else" excluding laboratory results - anything you can measure about a patient without removing a specimen from them.

This includes codes for vitals signs, hemodynamics, imaging, EKG, etc. as well as results from selected survey instruments (e.g PHQ-9 depression scale, CMS-required patient assessment instruments, etc.)

Examples

Deep Dive: LOINC code components

Each LOINC code description follows a regular schema with six components

These six parts care then translated into "LOINC names" to represent each concept. There are 3 different levels of specificity for LOINC names:

You can find more information about LOINC code parts here

Collection Codes

In addition to individual clinical findings, LOINC includes codes for common collections of findings, also known as "panels," "batteries," "surveys," or "questionnaires" depending on the clinical context.

Examples

You can find the constituent members of a collection by browsing loinc.org page for a collection's LOINC code and navigating "panel hierarchy" section.

Questionnaire Answers and Answer Lists

The ambition of LOINC is to standardize clinical data collection across organizations and clinical settings.

To standardize responses to questionnaires, LOINC provides standard codes not only for questions, but also to answer choices for multiple-choice questions. These LOINC codes are prefixed with LA, which stands for "LOINC Answer".

These answer choices are then bundled into 'answer lists', which are annotated with their own distinctive LOINC codes, prefixed with LL.

What's fantastic about the LOINC system is its intuitiveness. For instance, when you're browsing loinc.org and you view the code for a question, you're also shown any recommended answer values. This level of interconnectedness makes navigating and understanding the LOINC system that much more user-friendly.

Examples

Example: PHQ-4 Questionnaire

{
  "resourceType": "Questionnaire",
  "title": "Patient Health Questionnaire 4 item (PHQ-4) [Reported]",
  "status": "draft",
  "code": [
    {
      "code": "69724-3",
      "display": "Patient Health Questionnaire 4 item (PHQ-4) [Reported]",
      "system": "http://loinc.org"
    }
  ],
  "meta": {
    "profile": ["http://hl7.org/fhir/uv/sdc/StructureDefinition/sdc-questionnaire|2.7"]
  },
  "item": [
    {
      "type": "choice",
      "code": [
        {
          "code": "69725-0",
          "display": "Feeling nervous, anxious or on edge"
        }
      ],
      "required": false,
      "linkId": "/69725-0",
      "text": "Feeling nervous, anxious or on edge",
      "answerOption": [
        {
          "valueCoding": {
            "code": "LA6568-5",
            "display": "Not at all",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6569-3",
            "display": "Several days",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6570-1",
            "display": "More than half the days",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6571-9",
            "display": "Nearly every day",
            "system": "http://loinc.org"
          }
        }
      ]
    },
    {
      "type": "choice",
      "code": [
        {
          "code": "68509-9",
          "display": "Over the past 2 weeks have you not been able to stop or control worrying",
          "system": "http://loinc.org"
        }
      ],
      "required": false,
      "linkId": "/68509-9",
      "text": "Over the past 2 weeks have you not been able to stop or control worrying",
      "answerOption": [
        {
          "valueCoding": {
            "code": "LA6568-5",
            "display": "Not at all",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6569-3",
            "display": "Several days",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA18938-3",
            "display": "More days than not",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6571-9",
            "display": "Nearly every day",
            "system": "http://loinc.org"
          }
        }
      ]
    },
    {
      "type": "choice",
      "code": [
        {
          "code": "44250-9",
          "display": "Little interest or pleasure in doing things",
          "system": "http://loinc.org"
        }
      ],
      "required": false,
      "linkId": "/44250-9",
      "text": "Little interest or pleasure in doing things",
      "answerOption": [
        {
          "valueCoding": {
            "code": "LA6568-5",
            "display": "Not at all",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6569-3",
            "display": "Several days",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6570-1",
            "display": "More than half the days",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6571-9",
            "display": "Nearly every day",
            "system": "http://loinc.org"
          }
        }
      ]
    },
    {
      "type": "choice",
      "code": [
        {
          "code": "44255-8",
          "display": "Feeling down, depressed, or hopeless",
          "system": "http://loinc.org"
        }
      ],
      "required": false,
      "linkId": "/44255-8",
      "text": "Feeling down, depressed, or hopeless",
      "answerOption": [
        {
          "valueCoding": {
            "code": "LA6568-5",
            "display": "Not at all",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6569-3",
            "display": "Several days",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6570-1",
            "display": "More than half the days",
            "system": "http://loinc.org"
          }
        },
        {
          "valueCoding": {
            "code": "LA6571-9",
            "display": "Nearly every day",
            "system": "http://loinc.org"
          }
        }
      ]
    },
    {
      "type": "decimal",
      "code": [
        {
          "code": "70272-0",
          "display": "Patient health questionnaire 4 item total score",
          "system": "http://loinc.org"
        }
      ],
      "required": false,
      "linkId": "/70272-0",
      "text": "Patient health questionnaire 4 item total score",
      "item": [
        {
          "text": "The PHQ-4 is different -- although the total score (which ranges from 0-12) can be used, it is really a combination of the PHQ-2 depression scale (described above) and the GAD-2 anxiety scale (from the parent GAD-7 anxiety scale).  Thus, another way to look at it is a 0-6 depression subscale and a 0-6 anxiety scale. It is clearly different than either the PHQ-9 or the PHQ-2",
          "type": "display",
          "linkId": "/70272-0-help"
        }
      ]
    }
  ]
}