HIV prevalence in subpopulations of young people with high-risk behaviour

Export Indicator

The proportion of young members of defined subpopulations at high risk of contracting or transmitting HIV infection who test HIV-positive.
What it measures

This indicator is most useful in countries where HIV infection has not spread to the general population but remains concentrated in certain groups; however, it is essential to estimate the prevalence among commercial sex workers in generalized epidemics. This is because the prevalence in this group is likely to be considerably higher than among the general population, representing a «reservoir» of the virus within the generalized epidemic. The prevalence of HIV infection among members of these groups identifies important areas and groups for intervention. Trends in prevalence can indicate whether interventions are having an impact or whether some other factors are driving prevalence up or down. In a concentrated epidemic the groups of interest generally include one or more of the following: IDUs, MSM, sex workers and frequent clients of sex workers.

Rationale
Numerator

The number of young people participating in high-risk behaviour who test positive for HIV infection.

Denominator

The number of young people tested for HIV infection.

Calculation
Method of measurement

This indicator should be reported as percentages for males and females and the age groups 15–19, 20–24 and 15–24 years. Any data available on young people aged 10–14 years can also be given. The sample sizes should be given for each category and the HIV testing protocol should be given. It may be appropriate to give estimates disaggregated by the duration of the high-risk behaviour. In surveys conducted among groups with high-risk behaviour, sampling should not be restricted to young people. Instead, this indicator should be based on data from a subset of respondents. It is important that surveys among these groups cover a sufficiently large sample to provide reliable estimates for young people. If sample sizes are small and, as a consequence, such subdivisions would prejudice anonymity, or if information is not available on HIV status, it is not necessary to provide the prevalence data subdivided by age or duration of the high-risk behaviour. Instead, the age distribution of whole groups should be reported, regardless of HIV status. The groups can be described in the age groups

Measurement frequency
Disaggregation

Age group: 15 years - 19 years, 15 years - 24 years, 20 years - 24 years

Education: N/A

Gender: Male, Female

Geographic location: N/A

Pregnancy status: N/A

Sector: N/A

Target: Sex workers, Clients of sex workers, Injecting drug users, Men who have sex with men

Time period: N/A

Type of orphan: N/A

Vulnerability status: N/A

Explanation of the numerator
Explanation of the denominator
Strengths and weaknesses

A limitation of surveys among groups with high-risk behaviour is that it is not usually possible to find a representative probability sample. At best, this indicator represents the members of the subgroup with high-risk behaviour from which the sample has been drawn, and may not represent all persons displaying the behaviour. This means that it is difficult to estimate the extent to which an indicator based on these data describes prevalence among all members of the group. Information on the sizes of groups with highrisk behaviour is necessary in order to put these prevalence data in a national or regional context. Because of the difficulties of access to subpopulations the biases in subpopulation serosurveillance data are likely to be far greater and much less predictable than those in data from a more general population, such as women at antenatal clinics. Where sentinel sites provide health services to the subpopulation in question, for example, the use of the facilities may be associated with problems that are themselves related to HIV infection. It is especially difficult to minimize biases associated with age, since the age of participation in especially high-risk behaviour may be very variable. With regard to the explanation of observed patterns, chronological age is less important in groups with high-risk behaviour than the duration of the high-risk behaviour. It is essential, however, to collect and present data by age because this information allows the targeting of interventions and policies. Changes in HIV prevalence in these groups may reflect the success or failure of attempts to achieve prevention but they may also reflect changes in recruitment and exposure, which are unrelated to prevention efforts. This indicator should be considered in conjunction with the behavioural indicators that refer to the membership and activity of groups with high-risk behaviour, because changes in recruitment to or exit from the groups may be responsible for changes in observed prevalence. Prevalence is also affected by changes in the number of new infections and in mortality. Despite these difficulties it is essential to track HIV infection in people with high-risk behaviour in concentrated epidemics. The information cannot be perfect but some measure of progress or lack of it is essential for maintaining support for prevention programmes in critical subpopulations.

Further information