Customer Interface Requirements: Medication Data

Overview

Providing information about the customer interface requirements for FHIR resources which represent medication data pertaining to a Patient, namely:

• MedicationDispense

• MedicaionRequest

• MedicationStatement

Resource specific requirements

Dosages

All dosages must conform to the following requirements. If any of the below requirements do not satisfy your use case, please inform PKB and we can discuss expanding the capabilities to suit your needs.

• Only the first iteration of the dosage array is observed, all subsequent elements within the dosage array on all resource types will be ignored. “First iteration” in all instances is defined as the dosage element with a sequence equal to 1 or the first in the array if this is not present. Similarly, most subsequent information is derived from the first iteration of the doseAndRate array, with all subsequent elements within this array being ignored.

  • Multiple dosages with a sequence value of 1 is an error case.

  • If no dosage has a sequence value of 1, the first instance in the array is taken regardless of other sequence values. This means a dosage with a higher sequence value than those lower down in the array could be selected, depending on the data order.

• The dose value is derived from the first doseAndRate iteration, specifically the doseQuantity value element. doseRange is not currently supported.

• The dose unit is derived from the first doseAndRate iteration, specifically the doseQuantity system and unit elements. Both system and unit are mandatory.

  • You must provide a dose unit which is either UCUM or SNOMED CT, which means setting doseQuantity#system to either http://unitsofmeasure.org or http://snomed.info/sct respectively. UCUM is the standard preferred by the FHIR specification but there is a general acceptance within health interoperability that SNOMED is required to fulfil those units which represent non-UCUM values.

  • A data absent reason is permissible for the doseQuantity system in order to satisfy FHIR schema requirements, but note that this is strongly advised against as it renders the interpretation of the dosage unit vague and therefore liable to misinterpretation and clinical risk by the end user. See example below

  • This dose unit must be from the below supported list. If you wish to send in dose units which are not currently supported, please inform PKB and we can discuss expanding these capabilities to suit your needs.

  • UCUM dose units, as per specification requirements, are case sensitive. For millilitres, for example, mL is valid, ml is not.

  • The dose unit can be provided as either the doseQuantity#unit or doseQuantity#code elements. If both are provided, they must match. It is advised to provide the doseQuantity#unit element.

• The dose frequency is derived from the first dosage iteration and can be drawn from several elements on this complex subtype.

  • “As needed” is derived from dosage#asNeeded and set to true if asNeededBoolean is set to true. If the asNeeded element is a codeableConcept, as needed is always set to true. The contents of the codeableConcept are not observed for this purpose.

  • “As directed” is derived from dosage#timing#code and is set to true if this element is populated: as per the valueSet definition for this element, these are all a permutation of instruction to the patient. The specifics of the timing are not observed.

  • Specific frequencies (i.e. take this medication every 1 day) are derived from dosage#timing#repeat, specifically:

    • The frequency with which the medication is taken is derived from the period

    • The frequency unit is derived from the period unit

  • Other elements on the dosage#timing are currently not observed, such as dayOfWeek or timeOfDay

Example dose unit system absent

Supported dose units