A Guide to HIV/AIDS Epidemiological and Surveillance Terms

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Frequently Used Terms in HIV/AIDS Monitoring and Epidemiological Research in Canada

SELF-REPORTED DATA

In research studies, self-reported data is a term applied to information that is directly reported by the study participants.

Self-reported data may not always be accurate for several reasons. For example, in responding to questions about recent HIV-related risk behaviour

• a person may not always correctly remember all of the details of their past behaviours that may have placed them at higher risk of HIV;

• a person may choose not to report these details for fear of stigmatization or of a negative reaction from the interviewer;

• a person may exaggerate these details because they think that this may help or impress the interviewer.

As self-report is not always be the best method of collecting data, additional sources to verify self-report data are sometimes used.

SENTINEL SURVEILLANCE

Sentinel surveillance is a type of surveillance activity in which specific facilities such as offices of certain health care providers, hospitals or clinics across a geographical region are designated to collect data about a disease, such as HIV infection. These data are reported to a central database for analysis and interpretation.

These sources of surveillance information can provide information not otherwise available through positive HIV test reports and AIDS case reports. For example, information on specific populations, such as specific ethnic groups, may be gathered by sentinel surveillance.

SEROCONVERSION

The root “sero” means the serum or the watery portion of blood.

In HIV/AIDS research, seroconversion refers to the development of detectable antibodies to HIV in the blood as a result of HIV infection. A person who goes from being HIV negative to HIV positive is said to have seroconverted or is a seroconverter.

A seroconverter is a person who has had one or more HIV blood tests (repeat tester) with negative results and who then, as a result of HIV infection, receives a positive HIV blood test result. The initial negative serostatus has converted to positive serostatus.

Antibodies to HIV are the proteins the body produces in response to HIV infection. Once HIV antibodies have developed, they remain in the body for life.

SEROCONVERSION PERIOD
(See also SEROCONVERSION)

In HIV/AIDS research, the seroconversion period refers to the period of time it usually takes to develop detectable antibodies to HIV following infection with HIV. In 75% of persons, antibodies are produced in 4 to 8 weeks; in almost all persons, antibodies are produced within 14 weeks.

The seroconversion period is frequently described as the “window period”. It is very significant in relation to the timing of HIV tests. Persons who are tested during the window period may receive a negative HIV test result although they may be infected with HIV. Persons disclosing HIV-related risk factors in the 14 weeks before testing negative for HIV are encouraged to be retested at the end of the window period.

SEROCONVERTER
(Refer to SEROCONVERSION)

SERODIAGNOSTIC DATABASES

Most public health laboratories across Canada maintain serodiagnostic databases. In relation to HIV, these laboratories maintain a collection of information regarding the diagnostic results of all HIV blood tests. These databases monitor HIV subtypes and HIV mutations, and provide useful data regarding the characteristics and proportions of various groups, such as men who have had sex with men (MSM) and injecting drug users (IDUs), who test HIV positive.

SERONEGATIVE
(Refer to SEROSTATUS)

SEROPOSITIVE
(Refer to SEROSTATUS)

SEROPREVALENCE

The term seroprevalence refers to the prevalence or prevalence rate of a disease determined by testing blood rather than by testing saliva, urine, or sputum.

SEROSTATUS
(See also SEROCONVERSION)

The result of a blood test. The serostatus or blood test result of an individual tested for HIV can be HIV negative or HIV positive.

A person who tests positive for HIV through a blood test is considered to be seropositive for HIV. If that person tests negative, he or she is seronegative.

STATISTICAL SIGNIFICANCE
(See also CONFIDENCE INTERVAL)

Statistical significance is the degree to which the observed study result could have occurred by chance alone. This can be determined by the application of a statistical test to a set of data to generate a p value. Statistically significant results mean the study results are unlikely to be due to chance alone. P values are reported so that anyone using the data will know how much confidence to place in the reported results.

SURVEILLANCE
(See also FAQs 6, 7, 23)

Surveillance is the ongoing collection, analysis and interpretation of data about a disease such as HIV or about a health condition. The objective of surveillance is to assess the health status of populations, detect changes in disease trends or changes in how the disease is distributed, define priorities, assist in the prevention and control of the disease, and monitor and evaluate related treatment and prevention programs.

In Canada, many groups contribute to the surveillance of HIV/AIDS, such as research investigators and provincial and territorial laboratories. The Centre for Infectious Disease Prevention and Control (CIDPC) compiles and monitors many of these data, which it publishes in the HIV/AIDS Epi Updates and Surveillance Reports.

HIV/AIDS surveillance in Canada is conducted by the collection of AIDS case reports and positive HIV test reports as well as data collected through sentinel surveillance.

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