Fig. 3.

Unlinked anonymous programme methodology. The unlinked anonymous programme measures HIV prevalence among defined populations in the United Kingdom. Gay men attending genito-urinary medicine (GUM) clinics having routine syphilis tests are one of these populations. After testing there is leftover specimen, which has limited demographic and exposure data attached to it, as well as sexual orientation and whether known to be HIV infected. Before testing the leftover specimen for HIV, all patient identifiable information (e.g. name, DOB) are irreversibly removed making it impossible to identify from whom the specimen came. The sample is then tested and results from all samples are analysed and interpreted at a population level.