Download Medical monitoring: CD4 cell counts

medical monitoring: CD4 cell counts: 1
medical
monitoring:
CD4 cell counts
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Medical monitoring: CD4 cell counts
CD4 counts and HIV viral load are the best indicators so far discovered for monitoring the degree of damage to the
immune system from HIV and for the risk of clinical progression in AIDS. The clearest way to show that ARVs are
working to control HIV is through monitoring viral load before and during treatment.
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Slide 1
CD4 cell counts
(1)
■ CD4 cells are a type of white blood cell, or lymphocyte
■ CD4 cells are infected by HIV and die
■ Numbers fall as HIV disease worsens
■ Measured by blood test
■ Normal CD4 count in HIV-negative adult
■ Men: 400-1200 cells/mm3
■ Women: 500-1600 cells/mm3
■ CD4 cell count used to monitor progress of HIV disease
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CD4 cell counts
What is the CD4 count?
Lymphocytes are a subgroup of the body’s white blood cells (leukocytes). CD4 cells are one type of lymphocyte
and they co-ordinate the immune system’s response to certain micro-organisms, such as viruses. CD4 cells are the
main cells in the body infected by HIV. HIV causes the death of CD4 cells.
The CD4 count is measured by taking a small sample of blood (a cubic millimetre, or mm3). The count measures
the number of CD4 cells circulating in the blood sample, not the actual number of CD4 cells in the body.
A normal CD4 count in a person who is HIV-negative can range between 400 and 1600. Smokers tend to have
higher CD4 counts than non-smokers, and women tend to have higher counts than men. If a person is HIVpositive, the CD4 count can go up and down for reasons that have nothing to do with HIV infection. It can be
affected by the time of day that it is tested, by other infections such as colds and flu, by smoking, the seasons of
the year and in women, the menstrual cycle.
Changes in CD4 count
Changes in CD4 cell count are helpful to show the progression of HIV infection and the level of damage to the
immune system. Where CD4 testing is available, a series of CD4 test results should be used to make a decision
regarding antiretroviral therapy – a single test is not enough. A series of tests will provide much more information
about the state of the immune system. If access to CD4 testing is limited, the results of a single test should be
interpreted in light of clinical symptoms and other laboratory tests such as total lymphocyte counts.
It is best to have the CD4 count monitored at the same clinic and at about the same time of day whenever possible.
If the person has an infection such as flu or herpes, its presence may decrease the CD4 count temporarily. It is
usually better to delay a CD4 test until after the infection has passed.
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Slide 2
CD4 cell counts and prognosis
■ CD4 count falls by approx 60-100 cells per year in HIV+ person
■ CD4 500-200
increased risk of minor infections and of TB – medicine to prevent
bacterial infections may be given
■ CD4 below 200
increased risk of serious, life threatening infections – medicine to
prevent infections should be given eg cotrimoxazole
■ CD4 below 200 and symptoms
give ARV treatment if available
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CD4 count and prognosis
Immediately after HIV infection, the CD4 count is likely to fall several hundred cells below the previous normal level.
The extent of this early drop and the level at which it stabilises are markers for the future risk of developing
disease.
Most people with HIV find that their CD4 count usually declines over a number of years. Every decrease of 100
cells doubles the risk of developing AIDS. However, the risk of developing AIDS is changing over time as a result of
treatment advances and other factors.
A CD4 count between 500 and 200 indicates that some damage to the immune system has occurred. Whilst the
CD4 count remains above 200, the risk of developing most opportunistic infections is not high.
In resource-limited, high prevalence settings, there is an increased risk of developing an HIV-related pneumonia,
Pneumocystis carinii pneumonia (PCP) and bacterial infections. This occurs when CD4 cell counts fall below 500.
The World Health Organization recommends preventive treatment (prophylaxis) for PCP for all patients who are at
the stage of needing ART, using co-trimoxazole which also prevents cryptococcal disease and treats bacterial
infections.
When the CD4 count falls below 100-75 cells, prophylaxis may also be recommended against fungal infections and
against an infection called Mycobacterium avium intracellulare (MAI), using fluconazole.
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Slide 3
CD4 counts on treatment
■ CD4 counts also used to monitor success of treatment
■ CD4 cell count should rise sharply in first year of treatment, and
continue to rise more slowly as long as treatment controls HIV
■ In people receiving treatment, CD4 counts may fail to rise, or fall,
because:
■ The treatment has failed to control the virus
(this will be evident if the CD4 count has not risen and symptoms are still present)
■ The treatment has stopped controlling the virus
(this will be evident if the CD4 count has fallen below its previous level)
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CD4 counts on treatment
If viral load tests are not available, CD4 counts are also used to monitor response to ART and to decide on when it
is safe to stop prophylaxis for opportunistic infections.
In people receiving treatment, CD4 counts usually rise in two phases:
■
at first very rapidly, because cells are freed from the lymph nodes where they have been tied up by HIV,
and can travel to other parts of the body
■
then slowly and steadily while new cells are created
In people receiving treatment, CD4 counts may fail to rise, or fall, because:
■
The treatment has failed to control the virus (this will be evident if the CD4 count has not risen and
symptoms are still present)
■
The treatment has stopped controlling the virus (this will be evident if the CD4 count has fallen below its
previous level)
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Slide 4
CD4 cell counts
(2)
■ For people not on treatment, CD4 counts should be tested:
■ At minimum: before starting treatment
■ If resources allow: at HIV diagnosis and every six months to year to
check for rapid decline
■ On treatment: after six months, and then every six months.
■ If downward trend and no symptoms, check sooner to see if treatment
is failing
■ If symptoms: measure CD4 before changing to get baseline measure
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CD4 cell counts
Where CD4 counting is available, a test will be carried out before treatment (the baseline) and then every six
months. It may be repeated sooner if the result shows a fall in the CD4 count in the absence of any illness, to
check if this is a temporary change or if it is a trend indicating that treatment is failing.
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Slide 5
Alternatives to CD4 counts
CD4 percentage:
■ Proportion of lymphocytes that are CD4 cells
■ 40% = good health, 20% = advanced HIV
Total lymphocyte count:
■ More labs have the equipment to do this test
■ BUT: less accurate measure of immune system’s health
■ TLC of 1200 is roughly equivalent to CD4 of 200
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Alternatives to CD4 counts
CD4 percentage
Sometimes doctors assess the CD4 percentage – this is the proportion of all lymphocytes that are CD4 cells. The
normal level is 40% in HIV-negative people.. The CD4 percentage tends to decline as HIV disease progresses.
When it is below 20% it is thought to represent a risk of opportunistic infections equivalent to a CD4 count of about
200.
Some doctors argue that this is the most accurate CD4 test, although it is not very sensitive to small changes. It
can be very useful if the CD4 result is unexpected, for example a sudden drop. The percentage of all lymphocytes
usually decreases if the immune system is damaged by HIV.. If the percentage stays the same it is more likely that
the patient has an infection which the immune system is dealing with, and which caused the CD4 count to drop
temporarily.
Total lymphocyte counts as an alternative to CD4 tests
A total lymphocyte count (TLC) - which includes CD4 and CD8 cell numbers — can be done more cheaply than
CD4 counts, on a haematology analyser, which is cheaper and more readily available than a flow cytometer. TLC
can used as a surrogate for CD4 counts, when combined with clinical evaluation and WHO staging. Specifically,
WHO recommends that in someone who has a TLC of less than 1200/mm3 and symptoms of HIV-related disease,
ARV treatment should be considered as if they had a CD4 count of 200 or less. This is a sensible recommendation
to deal with situations where antiretroviral treatment should urgently be provided and where CD4 counts are not
available.
However, TLC can be a misleading substitute for CD4 counts in the pre-symptomatic phase of HIV disease,
especially when CD8 counts are elevated alongside reduced CD4 counts.
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Slide 6
Exercise: how do we explain to patients
How do we explain to patients:
■ Why the CD4 cells are counted?
■ What the doctor can learn from the CD4 cell count
when does it go down and when does it go up?
■ When the CD4 cells will be counted
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Exercise: how do we explain to patients
This exercise is intended for use in settings where CD4 cell counting will be used to select patients for treatment
and to monitor treatment.
Objectives
To test participants understanding of the key information on the use of CD4 counts in monitoring prognosis and
treatment
To help participants improve their skills in communicating this information to people with HIV, other health care
workers and the community they work with.
Actions
Divide the participants into small groups (preferably no larger than four or five people in each group) and ask the
group to come up with a short presentation on the CD4 count and why it is monitored. This can take any form the
group chooses – a role play, a drawing or poster for the clinic. Encourage the groups to use language they think
will be understood by their patients – it is not necessary to use technical language.
This presentation should explain:
■
Why the CD4 cells are counted?
■
What the doctor can learn from the CD4 cell count – when does it go down and when does it go up?
■
When the CD4 cells will be counted
Time
30 minutes for small group work, 30 minutes to feed back.
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Equipment
All participants need flipchart paper and a copy of the handout on the CD4 counts section of this training module.
Feedback
Ask each group to make its presentation and ask the rest of the group to comment, respectfully, on the content.
Draw attention to any inaccuracies that need to be corrected.
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