Unit 5
Overview
What this unit
is about
The periodic evaluation of surveillance systems for sexually transmitted infections (STIs), HIV or AIDS is necessary in order to maintain:
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a responsive and relevant system of monitoring shifting disease trends
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effective disease control and management interventions
This unit discusses how to conduct an effective evaluation with emphasis on evaluating the completeness, timeliness, and validity (or accuracy) of the data collected in the surveillance system.
Warm-up
questions
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List three aspects of a disease under surveillance that an effective surveillance system should monitor.
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List two methods to measure completeness of case reporting.
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List two methods to report the timeliness of case reporting.
Introduction
What you
will learn
By the end of this unit you should be able to:
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Describe three elements of a disease under surveillance that a surveillance system should monitor
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define three key surveillance system attributes
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list tasks for evaluating a surveillance system
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describe methods to measure the completeness, timeliness, and accuracy of your surveillance system.
Purpose of
public health
surveillance
Public health surveillance is conducted in order to describe a disease that is determined to be of public health importance. Surveillance is done to guide public health intervention (such as prevention, treatment, control).
Why
evaluate?
Once you’ve set up an HIV/AIDS surveillance system, you want to make sure that it remains effective as the epidemic shifts over time. If your system is no longer effective, you will not have the right information to control HIV/AIDS.
Describing public
health conditions
Public health surveillance is done to address important public health diseases so that effective control measures can be put into place. In order to describe the condition under surveillance, the surveillance system must be able to describe the condition by:
Describing the
person
The surveillance system should be able to describe the characteristics of persons affected by the condition in terms that are relevant to the condition. For HIV infection, these characteristics should include at least the following information:
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date of birth
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sex
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transmission mode.
Public health reporting may include collecting patient names. In those situations where a patient must be contacted by public health authorities, there must be some mechanism enabling this to occur. In addition, persons with HIV infection are diagnosed only once. In other words, patients are not cured of these conditions and, therefore, cannot be re-infected. For a country (or city or district) to have an accurate count of persons with HIV infection, there must be a mechanism in place that can distinguish previously reported persons from newly reported ones. Keep in mind that a person may be reported to the public health authorities more than once. This might occur if a patient changes the place where he or she receives medical care. Therefore, case reports of persons with HIV infection must include a case identification code (patient name or unique code).
The same code will be used throughout each country, and ideally throughout the CAREC member countries.
You might also consider collecting information on the following additional characteristics:
The decisions regarding which characteristics to gather information on will depend upon the setting in which surveillance is conducted. For example, in some countries, information on marital status is not considered necessary to understand who is affected by HIV/AIDS.
Describing place
Documenting information on where people with HIV/AIDS live is done by collecting information that describes where the patient lives and receives care at the time of diagnosis with HIV infection. This information includes:
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residence (e.g., city/district/country of diagnosis)
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facility of diagnosis (the type of facility as well as its name and address)
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facility that submitted the case report.
Describing time Monitoring trends in HIV tells us whether the epidemic is getting better or worse; monitoring trend in AIDS in the era of universal access to antiretroviral treatment tells us whether treatment efforts are effective in reducing morbidity. To accurately describe these trends, case reports of persons with HIV infection must include:
date of HIV diagnosis date of diagnosis of HIV advanced disease (WHO clinical stage 3) or AIDS (WHO clinical stage 4) date of case report.
The date of diagnosis is used to understand the actual trends in the disease while the date of report is used as a way of understanding the bias caused by delays in reporting. Both of these dates are necessary in order to evaluate your surveillance system. Collecting information specific to HIV/AIDS The HIV epidemic presents unique challenges to public health. For example, reports of persons with HIV infection tell us about persons who are infected and when they were diagnosed, but do not give us information on when HIV infection was actually acquired. Although there are now laboratory methods that can be used to narrow the time period during which infection was likely to occur, these are not routinely done in the Caribbean region.
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