emis schema

Available on backends: EMIS

This schema defines the data (both primary care and externally linked) available in the OpenSAFELY-EMIS backend. For more information about this backend, see "EMIS Primary Care".

To use this schema in an ehrQL file:

from ehrql.tables.emis import (
    clinical_events,
    medications,
    ons_deaths,
    patients,
    vaccinations,
)

many rows per patient

clinical_events

Each record corresponds to a single clinical or consultation event for a patient.

Note that event codes do not change in this table. If an event code in the coding system becomes inactive, the event will still be coded to the inactive code. As such, codelists should include all relevant inactive codes.

Columns

date date

snomedct_code SNOMED-CT code

numeric_value float

many rows per patient

medications

The medications table provides data about prescribed medications in primary care.

Prescribing data, including the contents of the medications table are standardised across clinical information systems such as SystmOne (TPP). This is a requirement for data transfer through the Electronic Prescription Service in which data passes from the prescriber to the pharmacy for dispensing.

Medications are coded using dm+d codes. The medications table is structured similarly to the clinical_events table, and each row in the table is made up of a patient identifier, an event (dm+d) code, and an event date. For this table, the event refers to the issue of a medication (coded as a dm+d code), and the event date, the date the prescription was issued.

Factors to consider when using medications data

Depending on the specific area of research, you may wish to exclude medications in particular periods. For example, in order to ensure medication data is stable following a change of practice, you may want to exclude patients for a period after the start of their practice registration . You may also want to exclude medications for patients for a period prior to their leaving a practice. Alternatively, for research looking at a specific period of interest, you may simply want to ensure that all included patients were registered at a single practice for a minimum time prior to the study period, and were registered at the same practice for the duration of the study period.

Examples of using ehrQL to calculation such periods can be found in the documentation on how to use ehrQL to answer specific questions.

Columns

date date

dmd_code dm+d code

one row per patient

ons_deaths

Registered deaths

Date and cause of death based on information recorded when deaths are certified and registered in England and Wales from February 2019 onwards. The data provider is the Office for National Statistics (ONS).

This table includes the underlying cause of death and up to 15 medical conditions mentioned on the death certificate. These codes (cause_of_death_01 to cause_of_death_15) are not ordered meaningfully.

More information about this table can be found in following documents provided by the ONS:

• Information collected at death registration
• User guide to mortality statistics
• How death registrations are recorded and stored by ONS

In the associated database table ONS_Deaths, a small number of patients have multiple registered deaths. This table contains the earliest registered death. The ehrql.tables.raw.core.ons_deaths table contains all registered deaths.

Tip

If you need to query for place of death, please note that this is only available in the tpp backend

Columns

date date

Patient's date of death.

underlying_cause_of_death ICD-10 code

Patient's underlying cause of death of death.

cause_of_death_01 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_02 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_03 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_04 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_05 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_06 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_07 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_08 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_09 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_10 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_11 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_12 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_13 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_14 ICD-10 code

Medical condition mentioned on the death certificate.

cause_of_death_15 ICD-10 code

Medical condition mentioned on the death certificate.

one row per patient

patients

Patients in primary care.

In the EMIS backend, this table also includes information about the patient's current practice registration. Historical practice registration data is not currently available.

Recording of death in primary care

In England, it is the statutory duty of the doctor who had attended in the last illness to complete a medical certificate of cause of death (MCCD). ONS death data are considered the gold standard for identifying patient deaths because they are based on these MCCDs.

There is generally a lag between the death being recorded in ONS data and it appearing in the primary care record, but the coverage or recorded death is almost complete and the date of death is usually reliable when it appears. There is also a lag in ONS death recording (see ons_deaths for more detail). You can find out more about the accuracy of date of death recording in primary care in:

Gallagher, A. M., Dedman, D., Padmanabhan, S., Leufkens, H. G. M. & de Vries, F 2019. The accuracy of date of death recording in the Clinical Practice Research Datalink GOLD database in England compared with the Office for National Statistics death registrations. Pharmacoepidemiol. Drug Saf. 28, 563–569. https://doi.org/10.1002/pds.4747

Columns

date_of_birth date

Patient's date of birth.

• Always the first day of a month
• Never NULL

sex string

Patient's sex.

• Possible values: female, male, unknown
• Never NULL

date_of_death date

Patient's date of death.

registration_start_date date

Date patient joined practice.

• Never NULL

registration_end_date date

Date patient left practice.

practice_pseudo_id string

Pseudonymised practice identifier.

• Never NULL

rural_urban_classification integer

Rural urban classification:

• 1 - Urban major conurbation
• 2 - Urban minor conurbation
• 3 - Urban city and town
• 4 - Urban city and town in a sparse setting
• 5 - Rural town and fringe
• 6 - Rural town and fringe in a sparse setting
• 7 - Rural village and dispersed

• 8 - Rural village and dispersed in a sparse setting

• Always >= 1 and <= 8

imd_rounded integer

Index of Multiple Deprivation (IMD) rounded to the nearest 100, where lower values represent more deprived areas.

• Always >= 0, <= 32800, and a multiple of 100

Methods

age_on(date)

Patient's age as an integer, in whole elapsed calendar years, as it would be on the given date.

This method takes no account of whether the patient is alive on the given date. In particular, it may return negative values if the given date is before the patient's date of birth.

View method definition

return (date - patients.date_of_birth).years

has_practice_registration_spanning(start_date, end_date)

Whether a patient's registration spans the entire period between start_date and end_date.

View method definition

return patients.registration_start_date.is_on_or_before(start_date) & (
    patients.registration_end_date.is_after(end_date)
    | patients.registration_end_date.is_null()
)

many rows per patient

vaccinations

This table contains information on administered vaccinations, identified using SNOMED-CT codes for the vaccination procedure.

Vaccinations may also be queried by product code using the medications table.

Vaccinations that were administered at work or in a pharmacy might not be included in this table.

Columns

date date

The date the vaccination was administered.

procedure_code SNOMED-CT code