Pre-requisites

In addition to the guidance on this page the guidance and requirement on the Generic Subscription API Requirements page SHALL be followed when using the NEMS subscription API.

Creating a Subscription

To create a subscription, a client MUST:

  1. construct a Subscription resource conforming to the EMS-Subscription-1 FHIR profile and additional population guidance on this page
  2. POST the constructed EMS-Subscription-1 resource to the NEMS FHIR endpoint on the Spine
POST /Subscription

Request Headers

The subscribing organisation MUST include the following HTTP request headers when making the call to the Create Subscription API endpoint:

Header Description
fromASID ASID of the system posting to the Subscription API
toASID ASID of the NEMS service
InteractionID Fixed value: urn:nhs:names:services:clinicals-sync:SubscriptionsApiPost

Additional information about standard headers and endpoints is available in the Spine Core specification.

EMS-Subscription-1 resource population

FHIR element Cardinality Requirement
status 1..1 The status of the subscription (initially this will always be “requested” until the subscription is reviewed and activated
contact 1..* Contact details for the subscription.

The first instance of the contact element within the Subscription resource SHALL represent the organization requesting the subscription. The element SHALL contain the organisation ODS Code which matches the MESH mailbox ID specified in the channel.endpoint element. The elements within the first contact element should be as follows:

“use” must have a fixed value of “work
“system” must have fixed value of “url
“value” must have the URL to the organization accessable via the ODS API, for example:
https://directory.spineservices.nhs.uk/STU3/Organization/[Org_ODS_Code]

Additional contact elements included within the Subscription resource will be stored and returned by when managing the subscriptions but will not be validated as part of the business rules.
end 0..1 End date/time for subscription if relevant (e.g. for a temporary subscription). If not provided the subscription will be perpertual and not expire.
reason 1..1 The reason for creating the subscription (human readable description). Used primarily for reviewing the subscription in order to make it active, and also for patients / services to review what subscriptions exist and why they were created.
criteria 1..1 Criteria to match events against for this subscription - see below for examples.
channel.type 1..1 The delivery channel to use to deliver the event to the subscriber (currently only “message” is supported).
NOTE: In this case “message” refers to the use of MESH for as a delivery channel.
channel.endpoint 1..1 The specific endpoint (initially MESH mailbox ID) to deliver to.
NOTE: The ODS code associated with the mailbox MUST match the ODS code within the first instance of the contact element of the Subscription resource.

Once submitted, additional metadata will automatically be added to the Subscription resource by the NEMS:

FHIR element Cardinality Requirement
id 1..1 Identifier for the subscription
meta.lastUpdated 0..1 Date the subscription was last updated
meta.versionId 0..1 The ID for the specific version of the subscription

The create request MUST NOT include the fields above, as they can only be added by the NEMS (see Create Example below).

Criteria Components

The criteria element of the Subscription will use the FHIR search string format using the following components. Information on the difference between explicit and generic subscriptions can be found on the Subscriptions Overview page.

Component Explicit Subscription Cardinality Generic Subscription Cardinality Description
/Bundle?type=message 1..1 1..1 This identifies that we are interested in events (which are sent as Bundles in FHIR), of type “message”
serviceType=[CODE] 0..1 0..1 This element identifies the service type making the subscription. Current accepted values are:

GP - GP Practice related services
CHO - Child Health Organisation related services
UHV - Health Visitor related services
EPCHR - Electronic Personal Child Health Record services
Patient.identifier=[IDENTIFIER] 1..1 0..0 This is used for Explicit Subscriptions for an individual patient. The [IDENTIFIER] is the NHS Number for the patient.

For example: “&Patient.identifier=http://fhir.nhs.net/Id/nhs-number|[NHS Number]
MessageHeader.event=[CODE] 1..* 1..1 This is the type of event to subscribe to (see the Event Types).

For example:
&MessageHeader.event=pds-birth-notification-1&MessageHeader.event=vaccinations-1&MessageHeader.event=pds-change-of-address-1

is an expression to specify events where the MessageHeader.event is of type “pds-birth-notification-1”, “vaccinations-1” or “pds-change-of-address-1”
Patient.age=[AGE] 0..2 0..2 This is a filter to only match events where the age of the patient (in years) meets the criteria supplied.

Examples:
- “&Patient.age=lt14
- “&Patient.age=gt60
- “&Patient.age=gt5&Patient.age=lt19

For more detail see the Search Parameter EMS Patient Age
subscriptionRuleType=[CODE] 0..0 1..1 This identifies the type of matching the NEMS will do between the patient demographics and the organisation code specified in the “Organization.identifier” criteria component. Current accepted values are:

GP_GP_GP - This will be a match if the patients registered GP matches the GP Practice code within the “Organization.identifier” criteria component.

UHV_POSTCODE_LACODE - This will be a match if the Local Authority Code responsible for the geographical location of the patients post code matches the code within the “Organization.identifier” criteria component.

CHO_GP_CCG - This will be a match if the CCG Code responsible for the geographical location of the patients registered GP matches the code within the “Organization.identifier” criteria component.

CHO_POSTCODE_CCG - This will be a match if the CCG Code responsible for the geographical location of the patients postcode matches the code within the “Organization.identifier” criteria component.

HSS - National subscription, subscription criteria is a match for any patients in England.
Organization.identifier=[CODE] 0..0 0..1 This element is required as part of the generic subscription to specify the organisation code which the NEMS will match to, based on the rule specified within the subscriptionRuleType criteria component.
tag=[tag_value] 0..1 0..1 The optional tag criteria element allows the subscriber to include a tag for the subscription that will be sent with the event message, when delivered through MESH, as outlined on the Event Receiver page.

The tag element value must only include
- letters ([a-z][A-Z])
- numbers ([0-9])
- hyphens (-)
- underscores (_)
- pipes (|)
- commas (,)

The tag value must contain a maximum of 100 characters.

Criteria Examples

Scenario Subscription Type Criteria String
A PHR system subscribing to change of address event for a specific patient registered for a PHR Explicit /Bundle?type=message&serviceType=GP&
Patient.identifier=http://fhir.nhs.net/Id/nhs-number|9434765919
&MessageHeader.event=pds-change-of-address-1
A child health service subscribing to change of address event for patients who’s postcode is within the catchment area of a CCG with the ID “X2458” Generic /Bundle?type=message&subscriptionRuleType=
CHO_POSTCODE_CCG&Organization.identifier=
X2458&MessageHeader.event=pds-change-of-address-1&tag=site123

Error Handling

If an error occurs when the NEMS processes the subscription request, a HTTP error status code will be returned along with an OperationOutcome FHIR resource within the payload. The OperationOutcome resource will contain one of the Spine ErrorOrWarning Codes and conform to the structure set out in the Spine Core FHIR specification.

Response

When a subscription request is successfully received by the NEMS, the Subscription will be assigned a logical ID and the NEMS will return:

  • a HTTP status code of 201 Created
  • a Location header containing the new logical ID of the created Subscription resource

No payload will be returned with the successful response unless the event message type being subscribed to is being deprecated.

Deprecation Warnings

In order for the NEMS to communicate to a subscriber that an event type is deprecated, the NEMS will include an OperationOutcome payload along with the successful 201 Created response, when the event type being subscribed to is due to be deprecated. More information about deprecation can be found on the Event Lifecycle and Deprecation.

The OperationOutcome resource will contain one or more issue elements, one for each event type which is being deprecated. The following elements, containing details of the event type deprecation will be populated:

Element Cardinality Description
issue 1..* One issue will be included for each event type which is being deprecated. Each issue may have a different code and supporting information.
issue.details.coding.code 1..1 The event life cycle warning type.
issue.diagnostics 1..1 Additional information about the event type deprecation including the date when the event will be deprecated and no longer supported by the NEMS and a URL where additional information about the event can be found.

Example:

<OperationOutcome>
   <issue> 
      <severity value="information"/> 
      <code value="informational"/> 
      <details>
         <coding> 
            <system value="https://fhir.nhs.uk/STU3/CodeSystem/Spine-ErrorOrWarningCode-1"/> 
            <code value="DEPRECATED"/> 
            <display value="The operation being performed has been deprecated"/> 
         </coding> 
      </details> 
      <diagnostics value="Deprecation of the Newborn Hearing (newborn-hearing-1) event type will occur on 22/06/2019, for more information go to https://developer.nhs.uk/apis/ems-beta/overview_supported_events.html"/>
   </issue> 
   <issue> 
      <severity value="fatal"/> 
      <code value="not-supported"/> 
      <details>
         <coding> 
            <system value="https://fhir.nhs.uk/STU3/CodeSystem/Spine-ErrorOrWarningCode-1"/> 
            <code value="NO_LONGER_SUPPORTED"/> 
            <display value="Event message type is no longer supported"/> 
         </coding> 
      </details> 
      <diagnostics value="Withdrawal of Event message type `pds-birth-notification-1` will occur on 01/01/2020, for more information go to https://developer.nhs.uk/apis/ems-beta/overview_supported_events.html"/>
   </issue> 
</OperationOutcome>

Create Subscription Example

HTTP request (explicit subscription)

POST https://clinicals.spineservices.nhs.uk/STU3/Subscription HTTP/1.1

<Subscription xmlns="http://hl7.org/fhir">
	<meta>
		<profile value="https://fhir.nhs.uk/STU3/StructureDefinition/EMS-Subscription-1"/>
	</meta>
	<status value="requested"/>
	<contact>
		<system value="url"/>
		<value value="https://directory.spineservices.nhs.uk/STU3/Organization/RR8"/>
		<use value="work"/>
	</contact>
	<reason value="Health visiting service responsible for Leeds"/>
	<criteria value="/Bundle?type=message&amp;serviceType=UHV&amp;Patient.identifier=http://fhir.nhs.net/Id/nhs-number|9434765919&amp;MessageHeader.event=pds-change-of-address-1" />
	<channel>
		<type value="message"/>
		<endpoint value="Mailbox1234"/>
	</channel>
</Subscription>

HTTP request (generic subscription)

POST https://clinicals.spineservices.nhs.uk/STU3/Subscription HTTP/1.1

<Subscription xmlns="http://hl7.org/fhir">
	<meta>
		<profile value="https://fhir.nhs.uk/STU3/StructureDefinition/EMS-Subscription-1"/>
	</meta>
	<status value="requested"/>
	<contact>
		<system value="url"/>
		<value value="https://directory.spineservices.nhs.uk/STU3/Organization/RR8"/>
		<use value="work"/>
	</contact>
	<reason value="Health visiting service responsible for Leeds"/>
	<criteria value="/Bundle?type=message&amp;subscriptionRuleType=CHO_POSTCODE_CCG&amp;Organization.identifier=X2458&amp;MessageHeader.event=pds-change-of-address-1" />
	<channel>
		<type value="message"/>
		<endpoint value="Mailbox1234"/>
	</channel>
</Subscription>

HTTP response

HTTP 201 Created
Date: Fri, 25 May 2018 16:09:50 GMT
Last-Modified: Fri, 25 May 2018 16:09:50 GMT
ETag: W/"25777f7d-27bc"
Location: https://clinicals.spineservices.nhs.uk/STU3/Subscription/ea0a485187204b49b978bdcf7102388c

Successful response with deprecation warning:

HTTP 201 Created
Date: Fri, 25 May 2018 16:09:50 GMT
Last-Modified: Fri, 25 May 2018 16:09:50 GMT
ETag: W/"25777f7d-27bc"
Location: https://clinicals.spineservices.nhs.uk/STU3/Subscription/ea0a485187204b49b978bdcf7102388c

<OperationOutcome>
   <issue> 
      <severity value="information"/> 
      <code value="informational"/> 
      <details>
         <coding> 
            <system value="https://fhir.nhs.uk/STU3/CodeSystem/Spine-ErrorOrWarningCode-1"/> 
            <code value="DEPRECATED"/> 
            <display value="The operation being performed has been deprecated"/> 
         </coding> 
      </details> 
      <diagnostics value="Deprecation of the Newborn Hearing (newborn-hearing-1) event type will occur on 22/06/2019, for more information go to https://developer.nhs.uk/apis/ems-beta/overview_supported_events.html"/>
   </issue> 
</OperationOutcome>
Tags: fhir