Background

The Chief Medical Officer (CMO) for England, working with the CMOs of the devolved administrations and other senior clinicians, commissioned NHS Digital to produce a list of vulnerable people at “high risk” of complications from COVID-19, who should be shielded for at least 12 weeks.

This list, originally referred to as the vulnerable patient list (VPL), has been renamed the Shielded Patient List (SPL).

The SPL list was defined as a subset of a wider group of people who may be “at risk”.

Specific advice applies to these groups, currently:

1. “At Risk” – a larger group (circa 19 million) normally at risk from influenza – should practice strict social distancing
2. “At high risk” – a smaller sub-group (circa 1.5 million), defined by CMO – should practice complete “shielding”

The purpose of this document is to describe the methodology that has been used to  identify patients who meet the high risk criteria due to their inclusion in one or more of the disease groups outlined in table 1.

The list of conditions that defined this cohort was signed off by the Chief Medical Officers of the four nations of the UK on 18 March 2020, and is listed in table 1 below.

1. Solid organ transplant recipients who remain on long term immune suppression therapy.

2. People with specific cancers:

   • people with cancer who are undergoing active chemotherapy or radical radiotherapy for lung cancer
   • people with cancers of the blood or bone marrow such as leukaemia, lymphoma or myeloma who are at any stage of treatment
   • people having immunotherapy or other continuing antibody treatments for cancer *
   • people having other targeted cancer treatments which can affect the immune system, such as protein kinase inhibitors or PARP inhibitors *
   • People who have had bone marrow or stem cell transplants in the last 6 months, or who are still taking immunosuppression drugs

3. People with severe respiratory conditions including all cystic fibrosis, severe asthma and severe COPD. 

4. People with rare diseases and inborn errors of metabolism that significantly increase the risk of infections (such as SCID, homozygous sickle cell). 

5. People on immunosuppression therapies sufficient to significantly increase risk of infection.*

6. People who are pregnant with significant congenital heart disease.

* entries marked with a star had some limitations in central data - see note below

Version 2.0 provided the updated version of the list, which has been amended as follows: 

• incorporation of data from general practice using flu indicators
• review of existing codes

• new updates to hospital episode statistics including moving from a two year, to a 14-year period
• removal of deceased patients

Version 3.0 and onwards used the specific SPL GPES extract as described in the Dataset usage section. 

From version 17.0 onwards the Detained Person’s SPL has been produced in parallel, applying the same methodology and using an identical GPES extract. Whilst the Detained Person’s SPL is kept entirely distinct from the main SPL, there is cross-referencing to ensure the complete medical history is considered by the underlying algorithm.   

For version 23.0 onwards, the Royal College of Paediatrics and Child Health (RCPCH) guidance has been implemented. This requires a different rule set for under 18s based upon clinical evidence from the COVID-19 pandemic.

Patients are divided into two groups in the guidance:

Group A

Group A lists conditions that require continued shielding. A child with a condition in Group A should be advised to shield.  

Group B

Group B lists conditions that require discussion between the clinician and the child and their family/carer to establish whether on a case by case basis continued shielding is required. A child in Group B should have a discussion with their clinical team to establish whether on balance of risks they should be advised to shield. Not all children and young people with conditions listed in Group B will need to shield. If following a discussion, they are advised not to shield, the child should maintain stringent social distancing.

There is a third group who are currently on the NHS SPL but are no longer regarded as clinically extremely vulnerable. 

Group A only is added by the national rule set. Other patients will continue to be added or subtracted by their clinician. RCPCH guidance has been implemented for those patients up to their 18th birthday, at which point they will be considered under adult guidance. For further details please refer to Tables 2 and 3.

In October 2020 NHS Digital received advice from the Chief Medical Officer that Down Syndrome and Chronic Kidney Disease Stage 5 needed to be included in the Shielded Patient List qualifying conditions.

From version 36.0 onwards these conditions were introduced, but the processing of new additions for Down Syndrome was suspended from version 37.0. NHS Digital undertook a review of coding anomalies and this has been published as a known issue, with associated action plan.

For SPL versions 44 and 46 cohorts have been identified by the University of Oxford Q-COVID algorithm. This added 1.53M patients in total to the Shielded Patient List.

In version 44 the first tranche of 819k patients was added to the Shielded Patient List. This represented the cohort aged 19 – 69 identified by the COVID-19 Population Risk Assessment.

In version 46 the second and final tranche of 713k patients was added by the Shielded Patient List. This represented the cohort aged 70 and over identified by the COVID19 Population Rick Assessment.

Please see link for further detail about which datasets have been used by the algorithm to identify Clinically Extremely Vulnerable cohorts:  COVID19 Population Risk Assessment

Clinical assurance has been sought from both medical and pharmaceutical professionals throughout the process of identifying patients for inclusion in the SPL.

The approach taken built in a number of safety checks. These included the principles to:

• reuse code lists which are already established in the system
• minimise burden to the system including GPs and IT suppliers
• keep to existing data flow pathways wherever possible to minimise risk

Existing data sets do not hold data in the form in which it was required for this purpose. Data is held in clinical codes which do not directly map to the requirements in the SPL.

Expert clinicians were asked therefore to ‘translate’ (or map) the clinical requirements of the list into the right subsets of coded information so that individual patients could be identified.

The clinical assurance undertaken was restricted to the translation of these cohorts to the data sets held within NHS Digital.

The general limitations of the approach were recognised throughout. These include:

• the use of centrally held administrative data to identify patients for an intervention that could cause harm.
• the inaccuracy of the underlying data
• the incompleteness of the underlying data
• the speed at which the list was required (within 48 hours) 

It was agreed that these limitations would be mitigated by local approaches, with clinical services able to add to the list locally.

In addition to the general limitations noted above, it was identified that a number of specific categories on the” High risk” list, could not be identified or fully identified by centrally held data. These are signified by a star (*) in the table above.

All code sets used for mapping clinical concepts, were derived from established clinically validated lists specifically the seasonal influenza code list (Annex G). 

This list is maintained in the SNOMED CT terminology, codes identified as relating to the “high risk” categories were mapped using validated tools, and manually rechecked.

Additional conditions identified specifically by the CMO’s office were then added to the final ICD code list (note these are absent form the SNOMED CT code list contained in Annex B)

1. The flu at risk list was reviewed and mapped to the CMO categories by three clinicians.
2. The resulting subset was mapped via validated tooling to ICD10 by a clinical terminologist using validated tooling.
3. The ICD 10 Code set was then manually re checked by two classification and terminology specialists and a clinician.
4. Additional conditions as specified by the CMO’s office were then added to this code set to produce the final list.