[Symbiote]

Isn't this a privacy issue? There are some very small GP offices. From the HSCIC FAQ:

    I am prescribed a drug for a rare condition; can I be identified in this dataset?

    All practice level information down to presentation level is being released, but no
    information about patients is contained in the data. It is not possible to identify
    individual patients in the data.
    In line with the recent High Court ruling on the release of abortion statistics, data can
    be released unless an individual can be identified from the data or from other data
    that is already in the public domain. The release of practice level prescribing data
    does not enable the identification of individual patients.
    If you are the only patient receiving a certain drug in your practice then the number
    of items prescribed and their cost for that medicine will be in this dataset but it will
    not show which patient received it. Note that information about the price of drugs is
    already available in the public domain.

That last paragraph doesn't make sense. I can easily imagine someone who knows a friend/relative has a rare condition using a data source like this to see how often it's being prescribed, and (perhaps) whether they're taking the medicine as often as they're supposed to.

[notahacker]

That was my first thought. I think it's brilliant that people with background knowledge can assess unusual prescription patterns at GP practices, but this is bound to release data that can give you a pretty good idea of [some of] what some individuals with a particular rare condition are being prescribed.

[tomjhill]

On your last point, you can actually tell the months when I didn't collect a prescription.