New Diagnoses of HIV - methods and frequently asked questions
Methods
Voluntary reports of HIV diagnoses in England, Wales and Northern Ireland are sent to the Health Protection Agency’s Centre for Infections. Reports are received from laboratories and clinicians. Laboratory report forms provide the initial information relating to HIV diagnoses. Subsequently clinician report forms contain much more detailed epidemiological information than laboratory forms and are essential in describing the HIV epidemic. For a variety of reasons, it is not always possible for a clinical report form to be completed (for example, the patient does not return to the clinic for their result) which is why it is essential that laboratories also report HIV diagnoses. Without information from laboratories we may underestimate the total number of HIV diagnoses. Clinician reports are also sent in the event of the first AIDS diagnosis or death in an HIV infected individual in England, Wales and Northern Ireland.
Inclusion Criteria: Who should be reported to the Health Protection Agency Centre for Infections
• All adults (15 years and above at diagnosis) diagnosed with HIV infection in England, Wales and Northern Ireland;
• All adults (15 years and above at diagnosis) with a first AIDS diagnosis in England, Wales and Northern Ireland;
• All deaths in HIV-infected adults (15 years and above at death) in England, Wales and Northern Ireland;
Exclusion Criteria: Who should not be reported
• Children (aged reported to the Institute of Child Health.
• Individuals newly diagnosed with HIV in Scotland, who should be reported to Health Protection Scotland.
Frequently asked questions:
- When presenting data by area do the numbers relate to a resident population?
- On occasions when presenting data by two levels of geography you sometimes state for the smaller level geography “Not known”, how can this be?
- Why are the variables “infection route / exposure group” and/or “country of infection” usually prefixed by “probable”?
- Aggregate data: the figure you report for the clinic/area I work within differs to the total number of diagnoses we have made at our clinic/area, why is this?
Is new HIV diagnoses data an estimate of incidence?
No - numbers include individuals who have an existing infection as well as those who have a newly acquired infection.
Is new HIV diagnoses data an estimate of prevalence?
No. Due to late reporting of deaths and individuals subsequently leaving the UK, an estimate of prevalence of diagnosed HIV infection cannot be gained by subtracting the number of deaths from the number of diagnoses. Numbers take no account of undiagnosed HIV infections in the population. Estimates of diagnosed prevalence can be attained from the Survey of Prevalent HIV Infections Diagnosed (SOPHID).
In the latest year there appears to be a flattening / decline in the observed number of new HIV diagnoses, is this representing a real decline?
Maybe. Due to reporting delay, data presented for more recent years will increase. Reporting delay can result in numbers slightly increasing for any previous years. For some overall totals we present adjusted numbers for more recent years which take account of reporting delay.
For more recent years some totals and sub-totals are presented by both the observed number of new HIV diagnoses and an adjusted number accounting for reporting delay. Why are not all totals and sub-totals adjusted for reporting delay?
It is possible to attain robust estimates for national totals and some sub-totals (for example, by prevention group). We are currently developing a statistical model that will allow us to present adjusted totals / sub-totals for specific countries / regions / Strategic Health Authorities.
When presenting data by area do the numbers relate to a resident population?
No. An area is defined by where an individual was first diagnosed (i.e. where the clinic or GP practice was located). There is evidence that a large proportion of individuals seek their HIV related care or treatment outside of their area of residence, with large cities in particular attracting individuals from outside of area. SOPHID provides residence and treatment based results for the diagnosed prevalent population.
On occasions when presenting data by two levels of geography you sometimes state for the smaller level geography “Not known”, how can this be?
For some diagnosing centres (particularly GP practices) with the available information it is possible to map to the larger area but not the smaller area.
Why are the variables “infection route / exposure group” and/or “country of infection” usually prefixed by “probable”?
It is often difficult to determine, both for the patient and their doctor, with certainty the route by which and the location where an individual acquired their HIV infection. Therefore the term “probable” is used.
Aggregate data: the figure you report for the clinic/area I work within differs to the total number of diagnoses we have made at our clinic/area, why is this?
The numbers we present refer to the number of new diagnoses in the UK. With some individuals receiving an HIV diagnoses at multiple sites (for example, due to transfer policy or re-testing) it is possible that some individuals reported to us from your site/area have already been entered on the system due to receiving a UK diagnosis elsewhere.
Disaggregate data: the figure you report for the clinic/area I work within differs to the total number of diagnoses we have made at our clinic/area, why is this?
It is possible that we may not have been able to enter some reports of diagnoses due to missing key fields (such as soundex, date of birth, sex and date of specimen); it is also possible that we have not as yet received reports that you have recently completed.
Last reviewed: 14 September 2009
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