You write that GPs will have to monitor substance misuse patients for criminal activity, as part of an England-wide audit (GP, 15 June).
The issue highlights the vulnerability of NHS records, where forensic information is already recorded and will be transferred into detailed care records and thence into the secondary uses database.
There is no intention that patients will be able to opt out of this (http://www.ardenhoe.demon.co.uk/privacy/decoy.pdf).
The problem is that despite all Connecting for Health's (CfH's) reassurances about the police not having direct access to the CfH database, there is nothing in the way the law is currently being applied to prevent the police applying their existing powers directly to the CfH database for information.
This might be information about an individual the police have already identified, which would be analogous to current practice.
Alternatively they could request that the database be searched to identify individuals who meet certain search criteria, for example: 'Please give us a list of cannabis users resident in a certain area who are white with a blood group of A+.'
Currently such an approach would have to be to the clinician or department who recorded the information and who would be more likely to apply the countervailing legal protections that do exist.
However, the size and incompleteness of locally held databases make it less likely that such requests will be generated.
With the national database, the police would be able to apply their powers to the least resistant of many users.
A government department is less likely to resist applications for information from other departments.
I hope this contextualises this important issue , which needs to be raised with the information commissioner's office.
Dr Paul Thornton, Kingsbury, Warwickshire.