# HealthLake Integrated NLP libraries
NLP libraries

HealthLake infers data found in the `DocumentReference` resource type using Amazon Comprehend Medical libraries. The Amazon Comprehend Medical API operations `DetectEntities-V2`, `InferICD10-CM`, and `InferRxNorm` detect medical conditions as *traits*. Each operation provides different insights.

**Language support**  
Amazon Comprehend Medical API operations only detect medical entities in English language texts.
+ **DetectEntities-V2**: Inspects the clinical text for a variety of medical entities and returns specific information about them, such as entity category, location, and confidence score.
+ **InferICD10-CM**: Detects medical conditions in a patient record as entities, and it links those entities to normalized concept identifiers in the ICD-10-CM knowledge base from the CDC's National Center for Health Statistics under authorization by the World Health Organization (WHO).
+ **InferRxNorm**: Detects medications as entities listed in a patient record, and it links them to the normalized concept identifiers in the RxNorm database from the National Library of Medicine.

The supported traits for each API operation are `SIGN`, `SYMPTOM`, and `DIAGNOSIS`. If traits are detected, they are added as FHIR-compliant extensions to different locations in your HealthLake data store. 

**Locations where extensions are added.**
+ `DocumentReference`: The results from the Amazon Comprehend Medical API operations are added as an `extension` to each document found within the `DocumentReference` resource type. Results in the extension are divided into two groups. You can find them in the results based on their `URL`.
  + `http://healthlake.amazonaws.com/system-generated-resources/`
    + These are resource types that have been created or added to by HealthLake.
  + `http://healthlake.amazonaws.com/aws-cm/`
    + Where the raw output of the Amazon Comprehend Medical API operations is added to your HealthLake data store.
+ `Linkage`: This resource type is either added or created as a result of the integrated NLP. A `GET` request on a specific `Linkage` returns a list of linked resources. To identify if a `Linkage` was added by HealthLake, look for the added `"tag": [{"display": "SYSTEM_GENERATED"}]` key-value pair. To learn more about the FHIR specifications for Linkage, see [https://hl7.org/fhir/R4/linkage.html](https://hl7.org/fhir/R4/linkage.html) in the **FHIR R4 documentation**.
+ FHIR resource types generated as a result of the Amazon Comprehend Medical operations.
  + `Observation`: includes results from the Amazon Comprehend Medical API actions `DetectEntities-V2` and `InferICD10-CM` when the traits are `SIGN` or `SYMPTOM`.
  + `Condition`: includes results from the Amazon Comprehend Medical API actions `DetectEntities-V2` and `InferICD10-CM` when the trait is `DIAGNOSIS`.
  + `MedicationStatement`: includes results from the Amazon Comprehend Medical API actions `InferRxNorm`.