Additions and subtractions

Version 3 introduced a mechanism whereby General Practice and NHS Trusts can “add” patients and Version 4 allowed General Practice to “subtract” individuals from the SPL. This is independent of disease coded data picked up by the algorithm and, for example, supports professional and clinical judgement by a GP or by a speciality consultant in a NHS Trust.

The mechanism for the additions and subtractions for hospitals, is by marking an individual record as either addition or subtraction in the appropriate field of the SPL Trust data collection template submitted via the Strategic Data Collection Service (SDCS) solution.

Additions and subtractions to the SPL from General Practice is managed through the use of the appropriate SNOMED CT Code as entered into the patients record, as follows:

The most recent code (determined by date of event where risk code is applied) will be used to determine a patient’s entry to, or removal from, the SPL.

Therefore, the methodology now follows the process below:

1. Data sources: GP clinical, hospital commissioning, primary care (dispensed medicines), maternity
2. Baseline SPL (algorithm only)
3. Additions and subtractions
4. Composite SPL

In the first instance, a date stamp (or event date) is attached to each record from source data that has triggered an addition to the baseline SPL. These data are collated in a fact table, or audit log.

The fact table includes 3 new data items, data source, risk flag and date. The risk flag is calculated as “High”, “Medium” or “Low”; or “H”, “M” or “L” for ease. 

For any record that triggers inclusion through the algorithm, the risk flag is set to “H” with appropriate data source and data also recorded.

Subsequent (non-algorithmic) additions and subtractions will be processed, by date, as follows:

In formulaic terms, actions and outcomes can be presented as follows:

The GP Clinical decision will always take priority in terms of subtractions and only newer eligible coded diagnoses will override this existing clinical decision. In practice this will only ever be from General Practice data, as HES data will generally be a period of time behind.

If there is a conflict in the SPL fact table between same dated methodology, a hospital or a GP update record, (i.e. diagnostic codes or risk codes have been applied with an identical date) the priority will be the GP clinical decision.

Patient opt-outs will be applied via General Practice.

As a final process step, when linking to the NHS Personal Demographic Service (PDS) dataset, the following adjustments will take place:

• deceased patients, both formally and informally marked, will be removed
• address and contact detail changes will be applied, based on latest demographic data
• individuals marked with a “Sensitive” flag in PDS will have all contact details removed from downstream data dissemination activity. However, these patients will remain present in the SPL
• if a date stamp is not attached to an event, then this will always concede precedence to dated events
• for congenital heart defects and pregnancy, the date for calculation will be the date of the defect
• no dates for drug data will be used for addition or subtraction processing i.e. GP or Hospital additions/ subtractions will always override groups which are modified by drugs, i.e. issuing a drug alone will not trigger re-entry onto the SPL