diff --git a/deploy/cttso-ica-to-pieriandx-cdk/Changelog.md b/deploy/cttso-ica-to-pieriandx-cdk/Changelog.md
index 8286ecb..7fb1369 100644
--- a/deploy/cttso-ica-to-pieriandx-cdk/Changelog.md
+++ b/deploy/cttso-ica-to-pieriandx-cdk/Changelog.md
@@ -15,6 +15,9 @@ are nested under deploy/cttso-ica-to-pieriandx-cdk.
   * Resolves https://github.com/umccr/cttso-ica-to-pieriandx/issues/146 
 * Use loc over iloc for pandas selection (https://github.com/umccr/cttso-ica-to-pieriandx/pull/154)
   * Resolves https://github.com/umccr/cttso-ica-to-pieriandx/issues/153
+* Replace mrn with external_subject_id for list of required fields (https://github.com/umccr/cttso-ica-to-pieriandx/pull/159)
+  * Resolves https://github.com/umccr/cttso-ica-to-pieriandx/issues/158
+
 
 ## 2023-10-18
 
diff --git a/deploy/cttso-ica-to-pieriandx-cdk/lambdas/layers/lambda_utils/globals.py b/deploy/cttso-ica-to-pieriandx-cdk/lambdas/layers/lambda_utils/globals.py
index ad86b7c..5408023 100644
--- a/deploy/cttso-ica-to-pieriandx-cdk/lambdas/layers/lambda_utils/globals.py
+++ b/deploy/cttso-ica-to-pieriandx-cdk/lambdas/layers/lambda_utils/globals.py
@@ -184,7 +184,7 @@ class SampleType(Enum):
     "date_received",
     "hospital_number",
     "gender",
-    "mrn",
+    "external_subject_id",
     "requesting_physicians_first_name",
     "requesting_physicians_last_name"
 ]