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HIV / AIDS
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Section 5: Screening for surveillance |
Surveillance testing is used to monitor the progress of the epidemic. This helps to ensure effective planning of health services and other services. Data from surveillance can be a powerful tool for lobbying for resources to be allocated to prevention and care activities, as well as helping to focus educational messages about prevention.
Surveillance is also important for monitoring the type of HIV that is prevalent in a particular area. Some sub-types of HIV may not be detected by some of the commercially available tests. If the HIV sub-type changes, the type of test used for diagnosis, blood screening and surveillance may need to change.
Even with anonymous and unlinked HIV screening for surveillance, care needs to be taken to maintain confidentiality. Care is also needed in deciding how to use the findings of surveillance studies. For example, if pregnant women or members of a particular community (such as soldiers) are tested, a high proportion are found to be positive and the results are made public, all members of these groups may be blamed for the spread of HIV. This is a danger, even though the individuals with HIV have not been named.
Pooling samples to reduce Costs
Pooling blood samples for testing (testing many samples together) can reduce the cost of surveillance studies in areas of low HIV prevalence. In rural Kenya, the National AIDS Control Programme evaluated the effect of pooling blood samples on cost and accuracy of results - 740 samples were tested individually and in pools of 10. The seroprevalence when measured individually was 7.3 per cent and when calculated from pooled testing was 7.49 per cent.
Pooling was practicable and reduced costs by 62 per cent with only slightly less accuracy. The researchers concluded that pooling made it cheap enough to carry out surveillance at district level. They concluded that pooling eight blood samples together would give give the best cost reduction and still be sufficiently accurate.
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