Data anonymisation at HIC

To maximise data security and data subject confidentiality HIC anonymises the data used for research using a project-specific anonymisation procedure.

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Project-specific anonymisation procedure

Step 1: Project dataset

Every project dataset will be uniquely anonymised before being made available to an Approved Data User, unless identifiable data is required and is specifically approved by the Data Controller.

Step 2: Pro-CHI

The Pro-CHI is generated by the HIC Data Analyst to uniquely anonymise a typical NHS dataset Community Health Index (CHI) number. This capability is located on a secure server, accessible only by the HIC Data Analyst and the System Administrator.

Step 3: Anonymisation process

The anonymisation process removes all names and addresses from the dataset.

As standard it also anonymises:

  • the CHI into a project-specific pseudo-CHI (Pro-CHI)
  • the date of birth – standard anonymisation is 3 months whereby the day will become ‘01’ and the month will become the middle of the appropriate quarter year e.g. 24/01/2005 will be anonymised as 01/02/2005
  • the postcode is restricted to postcode district / outward postcode only by removing the last 3 digits, e.g. DD1, DD10
  • the GP code, the GMC number (General Medical Council registration number), the GP Practice code and the Pharmacy code are all replaced by anonymous versions
  • if data is being provided via HIC Services that has already been effectively anonymised elsewhere, this procedure may not need to be repeated by HIC Services
  • where there is no CHI a unique pseudo-anonymised identifier will be allocated to each individual
  • aggregated data provided for study feasibility will not show values lower than five

These steps will help ensure that identification of individual patients is not possible, while retaining the ability to link patient data across multiple data sets for a particular project.

Step 4: Data request

Any request to the HIC Data Analyst for more detail about any of the Anonymised Data items listed above will be treated as a request for identifiable data, which will require study-specific Caldicott Guardian approval.

Step 5: Project specific

The Pro-CHI is project-specific ensuring that data provided to any one project remains within the bounds of linkage as approved for that project.

Step 6: Traceability

The Pro-CHI allows traceability of any HIC Services Project Dataset to the source of the data and the subsequent Approved Data User for that data. 


Christopher Hall
+44 (0)1382 383718