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Monitoring Immune Health
Two tests are used to monitor immune
health:
CD4Count test: This test
monitors the number of CD4 (or Helper T) cells in a blood sample.
This is expressed as a number of CD4 cells per cubic millimeter. A
single CD4 count test does little to determine one’s general state
of health. However, comparisons over time provide a better sense of
immune health by providing data by which to determine whether CD4
count is stable or declining. Three tests, given three to six months
apart, will be sufficient to determine a trend.
HIV Viral Load Test: This test
measures the amount of HIV genetic material (RNA or DNA) in the
blood. Viral load is often expressed as number of copies per
milliliter (mL). Two types of viral load test are currently
available, and they measure viral load in different ways. One test,
called the branched-chain DNA (bDNA) test, measures viral load by
causing the viral RNA in a sample to emit (give out) light; more
light means that more virus is present in the patient's blood. The
other test, called the reverse transcriptase polymerase chain
reaction or RT-PCR test (commonly called PCR), chemically multiplies
the amount of viral RNA in a blood sample, which makes it easier to
estimate the amount of virus in the body. A single viral load test is
not very meaningful; it must be considered along with other tests,
such as CD4 count, or compared to past viral load tests to be helpful
as an indicator of disease progression and immune health.
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