About the data for Wales

Codes used, data coverage and small number suppression.

Data disclaimer

Please bear in mind, BRIAN’s insights are a work-in-progress, and as such have not been fully peer-reviewed. Information presented through the insights is done without any implied warranty or fitness for purpose or use.

Data coverage

The data for our Welsh insights is based on individuals diagnosed with a primary brain tumour (restricted to the ICD-10 codes listed below). It comes from one of the following extracts held in the Secure Anonymised Information Linkage (SAIL) Databank:

  • Public Health Wales Welsh Cancer Intelligence and Surveillance Unit (WCISU) 01/04/2008 and 31/12/2017
  • NHS Wales’ Informatics Service Patient Episode Database for Wales (PEDW) 01/04/2008 and 30/10/2020
  • NHS Wales’ Informatics Service Outpatient Dataset (OPDW) 01/04/2008 and 31/10/2020
  • Office for National Statistics Annual District Death Extract (ADDE) 01/04/2008 and 31/10/2020

Respecting privacy

We take every care to ensure people's identities are protected when sharing data through our insights. We will only publicly share aggregated data. To ensure privacy, we apply some anonymisation methods to the results; we suppress small numbers from being displayed and we also round to the nearest five, in compliance with NHS ISB1523: Anonymisation Standard for Publishing Health and Social Care Data, the ICO Anonymisation Code of Practice, and the ONS Guidance for birth and death statistics.

'Small numbers' are classified in our insights as the numbers 1 to 7. Due to the filtering capabilities and the size of the datasets, our insights are likely to contain small numbers, which might facilitate identification of individual patients, especially at a local level. They might also allow identification of a specific hospital consultant, where local knowledge identifies a single consultant treating patients in a particular specialty. To avoid this, suppression rules are applied to our insights. ‘Small numbers’ after suppression will appear as ‘<7’. Zeros (0) do not need to be suppressed. All other counts will be rounded to the nearest 5. For example, numbers will appear after suppression as:

Before suppression 0 1 2 3 4 5 6 7 8 9 10 11 12 13
After suppression 0 <7 <7 <7 <7 <7 <7 <7 10 10 10 10 10 15
Before suppression After suppression
0 0
1 <7
2 <7
3 <7
4 <7
5 <7
6 <7
7 <7
8 10
9 10
10 10
11 10
12 10
13 15

ICD-10 codes used

Our Welsh insights use the following International Classification of Diseases, 10th revision (ICD-10) to identify brain tumour specific diagnoses:

C70.0, C70.1, C70.9, C71*, C72.0, C72.1, C72.2, C72.3, C72.4, C72.5, C72.8, C72.9, C75.1, C75.2, C75.3, D32.0, D32.1, D32.9, D33.0, D33.1, D33.2, D33.3, D33.4, D33.7, D33.9, D35.2, D35.3, D35.4, D42.0, D42.1, D42.9, D43.0, D43.1, D43.2, D43.3 D43.4, D43.7, D43.9, D44.3, D44.4, D44.5.

These are the same codes used for the English insights. They consist of all primary neoplasms (malignant, benign, uncertain or unknown behaviour) of the meninges, brain, central nervous system, and glands within the brain. Data on secondary tumours of the brain (metastases from other primary sites) is not included.

WHO ICD-10 Browser

Further information

Some of our insights use more specific sets of data.

Other conditions

This insight only includes ICD-10 codes from the following chapters:

Chapter I - Certain infectious and parasitic diseases
Chapter II - Neoplasms
Chapter III - Diseases of the blood and blood-forming organs and certain disorders involving the immune mechanism
Chapter IV - Endocrine, nutritional and metabolic diseases
Chapter V - Mental and behavioural disorders
Chapter VI - Diseases of the nervous system
Chapter VII - Diseases of the eye and adnexa
Chapter VIII - Diseases of the ear and mastoid process
Chapter IX - Diseases of the circulatory system
Chapter X - Diseases of the respiratory system
Chapter XI - Diseases of the digestive system
Chapter XII - Diseases of the skin and subcutaneous tissue
Chapter XIII - Diseases of the musculoskeletal system and connective tissue
Chapter XIV - Diseases of the genitourinary system.

More information on ICD-10 codes

Information about the SAIL databank

The Welsh insights in BRIAN use anonymised data held in the Secure Anonymised Information Linkage (SAIL) Databank. The relevant primary publications which describe SAIL are as follows:

  • Jones KH, Ford DV, Jones C, Dsilva R, Thompson S, Brooks CJ, Heaven Ml, Thayer DS, McNerney CL, Lyons RA. A case study of the Secure Anonymous Information Linkage (SAIL) Gateway: a privacy protecting remote access system for health related research and evaluation. Journal of Biomedical Informatics: special issue on medical data privacy 2014.
  • Ford DV, Jones KH, Verplancke JP, Lyons RA, John G, Brown G, Brooks CJ, Thompson S, Bodger O, Couch T, Leake K. The SAIL Databank: building a national architecture for ehealth research and evaluation. BMC Health Services Research 2009;9:157 http://www.biomedcentral.com/1472-6963/9/157
  • Lyons RA, Jones KH, John G, Brooks CJ, Verplancke JP, Ford DV, Brown G, Leake K. The SAIL databank: linking multiple health and social care datasets. BMC Medical Informatics and Decision Making 2009; 9:3. http://www.biomedcentral.com/1472-6947/9/3
  • Rodgers, S.E., Demmler J., Dsilva R., Lyons R. Health and Place. 28 Sept 2011, Protecting health data privacy while using residence-based environment and demographic data. Health and Place doi: 10.1016/j.healthplace.2011.09.006 https://www.ncbi.nlm.nih.gov/pubmed/21996431
  • Rodgers SE, Lyons RA, Dsilva R, Jones KH, Brooks CJ, Ford DV, John G, Verplancke JP. Residential Anonymous Linking Fields (RALFs): a novel information infrastructure to study the interaction between the environment and individuals' health. Journal of Public Health (Oxf). Dec 31 (4): 582-588, 2009.

Filters available

Our insights provide filtering capabilities; the filters available for each insight depend on the source data that drives our insights. Each is explained below.


To protect patient identity, age is grouped into ranges; the age ranges will vary for each insight.


The sexes available for filtering are 'male', 'female' and 'all'.

Tumour behaviour

The tumour behaviours available for filtering are 'benign', 'malignant', 'all' and 'not known' (unknown or uncertain behaviour).

Please note that when selecting to filter by ‘benign’ or ‘malignant’, insight data will include:

  • patients who have only ever been diagnosed with a tumour which matches the filter selected
  • those who’ve had multiple tumour diagnoses, where at least one diagnosis matches the filter selected.

This means anyone with a single tumour where the behaviour has changed, or anyone with more than one tumour, each with a different behaviour, will be included.


The years available in our insights are calendar years unless otherwise specified. The years available will vary depending on the source data for each insight.