Context for the Master Person Service (MPS)

The Master Person Service (MPS) is operated by the Spine team. It takes the demographic information contained in a person’s health and care records and matches it to their unique NHS number held in PDS to confirm their identity.

The matching or linkage process is comprised of several steps of increasing computational intensity, designed to address the challenges provided by data sets of different degrees of quality.

The outcome of the search might be an NHS number if the record was matched in PDS, an MPS_ID if the record was matched with previously unmatched records. If neither search was successful, a one-time-use ID is generated in DPS. DPS then transforms these into the Person_ID field.

MPS is exclusively used by DPS; data sets are batch-processed and enriched of the Person_ID field and possibly other fields (depending on the needs of the data asset).

There are other services in NHS England that support the retrieval of patients’ NHS number and other demographic information (for example, live services used in direct care). These, however, do not use MPS, but separate services which rely on similar tracing algorithms.

MPS uses the Personal Demographics Service data set (PDS); PDS is the national electronic database of NHS patient details, which holds about 80M records. The demographic details are normally updated when patients visit their GP but may also be updated by other healthcare professionals. This is therefore a “live” database as it changes daily. Data on PDS helps care providers to confirm the identity of patients, link their care records within an organisation and between different organisations, and to communicate with patients.

MPS uses PDS as the source database against which other data sets are compared for a match. In other contexts, PDS is sometimes referred to as a “service”, but in the context of MPS (and this document), PDS is referred to as a “database”.

The data items held include NHS number, name, date of birth (DOB), gender, GP practice, addresses (including historic addresses and postcodes) and contact details (such as telephone numbers and email addresses). Data is also held, where applicable, on certain patient preferences such as nominated pharmacy and whether the record is marked as 'sensitive'. No clinical data is held on the PDS. The full list of data items held on the PDS, along with other information about PDS, can be found on the Personal Demographics services web pages. 

The National Back Office (NBO) provides a national data quality service, responsible for resolving incidents with patients' demographic records in the PDS. NBO services include the identification of duplicates, confusions and changes of identity (for example, in adoptions and gender reassignment cases where a new NHS number has been assigned to the same person). The Demographics and NBO teams work closely together on investigations of more complex incidents and issues. 

NHS numbers are a national patient identifier within the UK’s health and social care system. The official list of individuals’ NHS numbers is held within PDS. The NHS numbers are allocated to new born babies soon after birth, and to individuals that are registered for NHS care in England, Wales or the Isle of Man. However, some individuals do not have one, for example, overseas visitors, long-term mental health patients and private patients.

The Person_ID derived via MPS uses the NHS number when this is available but creates an alternative key when the details of an individual are not found within PDS.

Hospital Episode Statistics (HES) consists of three databases containing all admitted patient care (APC) admissions, outpatient appointments (OP) and accidents and emergency (A&E) attendances at hospitals in England.

This is a well curated data asset, and most records in HES data sets have NHS number and DOB populated. This means that Person_ID matching is mostly based on the first, simplest and most robust tracing step in MPS, that is, cross-check trace.

HES data sets do not include patient names (surnames or forenames). As a result, the only other tracing step that can be used on HES is the algorithmic trace as the alphanumeric trace step must use names.

Data sets may have had their own methods of assigning a person identifier, and custom linkages based on combinations of data items may have been in use prior to data sets adopt the Person_ID. In HES, for example, Person_ID has replaced the use of HES_ID. Individual assessments of impacts of the adoption of Person_ID are undertaken on a case-by-case basis and published on the Methodological changes page (see Announcement of methodological change to HES).

Notably, HES runs through MPS after each submission and refreshes the Person_ID with the most up to date data available.