Table 1. Full list of variables included in the OpenSAFELY-TPP high-cost drugs dataset.

Variable name	Variable type	Specification details	Variable description
Patient_Id	n10	Mandatory where relevant	Pseudonymised patient identification, used to match dataset to other datasets within OpenSAFELY-TPP.
Financial Month	Max an2	Mandatory	Currently able to query in OpenSAFELY-TPP study definition Financial month the prescribed item was administered to patient. 1 = April; 12 = March
Financial Year	an6	Mandatory	Currently able to query in OpenSAFELY-TPP study definition Financial year the prescribed item was administered to patient. FY 2018/19 = 201819
PersonAge	n	Derived	Age of patient when prescribed item was administered to patient. Some submissions included age at intervention. Where missing this variable was derived using clinical intervention date and date of birth.
Person Gender	an1	Mandatory where relevant	Gender as stated by the patient. 1 = Male 2 = Female 9 = Indeterminate (unable to be classified as either male or female)
Activity Treatment Function Code	an3	Mandatory where relevant	Code to describe the clinical area that prescribing is taking place in, based on main speciality. Full list of codes found online 10 .
Therapeutic Indication Code	Min an6 Max an20	Mandatory where relevant	Should be a SNOMED CT Code but looks like input varies based on organisation collecting the data. Code used to identify the reason for administering drug to the patient.
HighCost TariffExcluded DrugCode	Min an6 Max an20	Optional	Should be a SNOMED CT Code but looks like input varies based on organisation collecting the data. This should be the dm+d description of medicine administered to patient. Only populated when the provider has a dm+d enabled system.
DrugName	Max an255	Mandatory where relevant	Currently able to query in OpenSAFELY-TPP study definition Input standardisation is at a provider level rather than a national level - non-standardised text input. The name of the prescribed item. Where possible this should be the SNOMED CT name. For drugs not listed in dm+d, this must be the valid name in UPPER CASE.
RouteOf Administration	Min an6 Max an20	Mandatory where relevant	Should be a SNOMED CT code but looks like input varies based on organisation collecting the data. To be populated by providers with an e-prescribing system.
DrugStrength	Max an100	Mandatory where relevant	The amount of ingredient substance in the prescribed item.
DrugVolume	Max an100	Mandatory where relevant	The volume of the drug administered to a patient when given in liquid form.
DrugPackSize	Max an100	Optional	The amount of product in a pack or container.
DrugQuanitity OrWeight Proportion*	Max n4.	Mandatory where relevant	The quantity prescribed in terms of either the packsize or number of doses. * To note, the variable name is misspelled.
UnitOf Measurement		Mandatory where relevant	Should be a SNOMED CT code but looks like input varies based on organisation collecting the data. Describes what the DrugQuanitity Or WeightProportion variable is measuring.
Dispensing Route	an1	Mandatory where relevant	Describes where the prescription item was dispensed to the patient. 1 = Inpatient (via internal pharmacy) 2 = Outpatient (via internal pharmacy) 3 = Outsourced pharmacy 4 = Homecare delivery 5 = Community pharmacy (FP10) 6 = Other (not listed)
HomeDelivery Charge	Max n18. Max n8	Mandatory	The amount charged for delivery of items to the patient's home.
TotalCost	Max n18. Max n8	Mandatory	The total cost of the activity that includes any agreed adjustments.
Derived SNOMED FromName	Max an255	Derived by NECS	dm+d code Over 90% NULL values (see Table 2).
DerivedVTM	Max an255	Derived by NECS	dm+d code - virtual therapeutic moiety Around one third of values are NULL (see Table 2).
DerivedVTM Name	Max an255	Derived by NECS	dm+d name - virtual therapeutic moiety Around one third of values are NULL (see Table 2).