I am responding to the posting of Dr. Roy Chan which describes an innovative
HIV testing program in Singapore that should lead to earlier detection
of HIV. In general, there are two major reasons for HIV testing, both involving
early detection community surveillance and individual diagnosis. Surveillance
is most often done with testing of sentinel groups, who serve as early
warning that HIV has started to appear in the community. There is no reason
for personal identification in such systems, since the intent is to warn
the community, and not diagnose individual infection. An analogous situation
is sampling of river water for signs of fecal contamination. Cups are dipped
in the water at various locations, and are tested for coliform agents.
If the coliform count is high, the river is deemed polluted and a warning
goes out to the neighboring communities. No one demands that sampling cups
be treated, since people recognize that such treatment of cups will not
have any impact on the expansive river.
In the same way, identifying and treating persons who are found to be
positive in sentinel surveillance programs will have little impact on HIV
in the community. But what harm can come of such identification in sentinel
surveillance programs? If those at "highest risk" among sentinel groups
avoid participating in the sentinel surveillance program because they fear
being identified, then the observed prevalence of HIV will be artificially
low, giving the community a false impression that all is well. For doing
such anonymous surveillance testing, saliva is an especially useful medium.
It is non-invasive (people don't like being stuck with a needle) and can
be collected by non-medical personnel who likely are more trusted by members
of the risk groups, and also are less expensive to employ.
Dr. Chan in his Singapore posting focused on testing done at the individual
level. Here the intent is to warn individuals early that they are infected,
so that they can:
start treatment, if therapeutic drugs are available,
avoid opportunistic infections such as tuberculosis that might lead to
know to take zidovudine if pregnant to avoid transmitting the virus to
know to stop breastfeeding also to avoid transmission to the nursing infant,
know to take protective measures to avoid transmitting the virus to sexual
partners or persons exposed to their blood.
So there are really two purposes for diagnostic testing, one being medical
and the other being public health. Early detection is important for both.
Testing schemes have to be developed that warn HIV persons early that they
are carrying the virus, and need to do something about it. Typically people
first have to be screened, and then those who screen positive are given
additional tests that confirm the diagnosis. Such screening and confirmatory
testing can be done in the same medical setting, offering counseling and
care along with testing. Here the name of the patient is known to the doctor,
but the diagnosis is treated as confidential to preserve the integrity
of the doctor-patient relationship. When doctors see their patients often,
they can include HIV testing as a routine component of their physical examination.
By doing so, they would detect HIV early, and be able to provide appropriate
medical care. Since most people do not see their doctors on a regular basis,
the screening function must be done by other means.
One such method being used in Singapore is an anonymous testing center
where people can go and get their screening results, without having to
share their name with those administering the clinic. In such settings it is important to be friendly and responsive, giving
people what they want and doing so quickly.
Such clinics also provide confirmatory testing, but for me that task
is not as important as the screening function. Anonymous testing centers
are useful if they are able to encourage those who screen HIV positive
to visit their doctor and seek both confirmatory testing (if not already
done) and medical assistance. Names are not necessary, but some indication
of care-seeking action is needed. Here is where research can help. Studies
might be done in various countries to determine if anonymous testing centers
actually notify people of the results, and if so, what do the HIV positive
people do about it.
Here in Los Angeles, we found that HIV testing programs
that were done at government STD clinics where collecting blood specimens,
doing the test, but not getting the results to about half all HIV infected
persons. One major reason was that people were not returning for their
results, given out one week later. The Singapore group apparently sensed
the same problem and switched to immediate testing kits so that people
could be told their screening status in one visit. This is very innovative,
and should be tried by others in Asia.
Finally to promote early detection, another form of screening is being
tried in the United States. Here we sell home collection kits, also for
anonymous use. People purchase the kit, submit a blood specimen by fingerstick
on a card, and send it to a laboratory for testing.
Three to seven days later they call for the results along with counseling.
The system seems to be working reasonably well, although one of the two
companies that are now licensed to sell such tests recently withdrew from
the market. The other company seems happy to be free of competition and
has its product available in drugstores throughout the nation.
In the future, consumers will probably favor such screening by saliva
rather than a fingerstick, and will want the results immediately, rather
than have to send the specimen to a laboratory and wait for several days.
Such immediate saliva tests, however, are not yet licensed in the United
Similar to their medical colleagues, public health officials should
favor early HIV detection. By finding carriers earlier in the course of
their infection, they can inform them of what needs to be done to avoid
transmitting the virus the others. Such information is especially important
for both husband and wife to share. For example, if the wife does not know
that the husband is infected, she will not encourage him to use condoms
during every coitus. Without such knowledge she might wonder why he wants
to use condoms at home, and certainly would not be supportive. Also in
the future when microbicides become available, she would not know to use
them. If the wife is infected and does not tell the husband, she also might
be reluctant to start treatments that would prevent perinatal transmission,
or to stop breastfeeding.
The net result of such silence is more viral transmission, giving the
rightful impression that public health is failing. To resolve this issue,
public health officials need to know the names of those who are infected.
They then need to notify married partners of infection in their household.
Since such notification can lead to many personal and social problems,
establishing such partner notification programs usually is done after extensive
consultation and with careful evaluation. Unfortunately, at present there
are far too few partner notification programs in Asia, thereby limiting
the public health benefits of early detection at the individual level.
For those planning to attend the Fourth International Congress on AIDS
in the Asia and the Pacific, being held this coming October in Manila,
Philippines, there likely will be much discussion about early detection
issues, including screening efforts, diagnostic and treatment program,
surveillance systems, and partner notification programs. Perhaps the Singapore
delegation will have more to say about their interesting anonymous testing
program at this meeting.