—EXPERTS CALL IT: “Lymphocyte Subset Panel 4” —IT TELLS YOU: How your immune system is doing —TAKE IT: As soon as you test positive, then every three to six months. When on HAART, every three months. —RESULTS IN: 2 weeks
Lo Talks: Michelle’s absolute CD4 count went from 497 in December 2002
to 1,062 in April 2003. “I was ecstatic,” she recalls. “A previous
doctor told me they would never go above 500. I believed him.” And at a
strong 0.63, her CD4/CD8 ratio was icing on the cake!
Lymphocyte Subset Panel 4 is chock-full of figures. But unless you’re
having a Marcus Welby, MD, moment, focus on two: the absolute CD4 count
and the CD4/CD8 ratio. Both speak volumes about your immune
BACKSTORY The white blood cells known as CD4s come in
“families,” with each line primed to battle a specific type of
infectious invader. Think of these cells, a.k.a. “helper T cells,” as
the generals that organize the armies of CD8s, a.k.a. “killer T cells.”
makes HIV so dangerous is that it breaks into these CD4s, takes over
operations and multiplies like mad, killing the cells. As HIV
progresses, fewer generals are left to run the war. (If, say, every CD4
in the “family” that combats PCP pneumonia is wiped out, your body
loses the ability to keep PCP at bay.) This is why your CD4 count is
such a useful indicator of immune health.
COUNT ‘EM UP! An
average healthy person clocks in with about 1,000 CD4s per tiny cubic
millimeter of blood (though “healthy” can range from 500 to 1,600). For
most HIVers, a count of 500 reflects wear and tear on the immune
system, but it’s no cause for panic—or necessarily for treatment. If
you go below 200, however, it’s time to start, restart or adjust your
SET A DATE As soon as you test positive, get those
CD4s counted. Then, once you start HAART, go down for the count every
three months (along with a viral load test).
A number of factors can skew results, so if yours are unexpected, you may want to retest in two to three weeks.
have blood drawn at the same time of day and use the same lab for every
test. If you’re on a drug holiday or you’ve recently switched regimens,
your doc may order monthly tests.
RATIO MATTERS Because it
fluctuates less than CD4 count over time, CD4/CD8 ratio is perhaps the
best lab measure of overall immune health. To get your ol’ reliable
ratio, your doctor simply divides your CD4 count by your CD8 count.
tend to have a ratio above 0.88. HIVers tend to have lower ratios
because they have fewer CD4s—and more killer CD8s—than healthy folks. (Experts haven’t determined why HIVers have more “killers”; that’s why stand-alone CD8 counts don’t tell much.)
you start meds, expect your CD4 count to rise—but your CD8s to fall!
That’s because as the virus in your blood decreases, your immune system
can send some of its fighting CD8s for some R&R.