Is there a doctor in the house?

February 5, 2008 6:00 AM

Calling ikkyu2: How is a clinical diagnosis of AIDS (as distinct from HIV infection) made?

A question for ikkyu2 and the other physicians on MeFi: How does an MD distinguish between a diagnosis of HIV infection and AIDS? Is it based on CD4+ count or is the diagnosis based on something else altogether, like the presence of opportunistic infection(s)? Forgive my ignorance and thanks in advance for any replies.

posted by inoculatedcities to science & nature (6 answers total)

Here is what you want, the CDC classification system.

The short answer is that CD4 count and presence of OIs are both used as indicators of AIDS. The thing to remember is that if someone is once diagnosed with AIDS, they are always considered to have AIDS, even if their CD4 count goes back up or the OI resolves. So it isn't present count that matters, it's nadir.

(I'm not a doctor, but I work in an HIV clinic.)
posted by OmieWise at 6:23 AM on February 5, 2008

Yea, my biochemistry classes taught that AIDS classification is based solely on your CD4 cell count. The idea is that CD4 cells are HIV's primary target- cells which are necessary for proper immune system defense. When your CD4 count gets below a certain level, you immune system is compromised.
posted by jmd82 at 6:51 AM on February 5, 2008

jmd82 is wrong. It's possible to be diagnosed with AIDS with a CD4 count above 200 if you are diagnosed with an AIDS defining condition per the CDC chart I linked to. I have AIDS patients in my clinic whose CD4 counts have never dipped below 250.
posted by OmieWise at 7:12 AM on February 5, 2008

OmieWise beat me to it.

There's no creativity or room for interpretation of these criteria; they are pretty cut and dried. The patient has to have a positive HIV test of some kind. Then, either a CD4 count below 200, or the presence of any one of a number of AIDS-associated diagnoses, (or both together) buys you the diagnosis of AIDS.
posted by ikkyu2 at 7:38 AM on February 5, 2008

OmieWise has it. An AIDS diagnosis is based on HIV AND EITHER a CD4 count below 200 OR an opportunistic infection on the CDC list linked to above.

And while there is still some vague epidemiological reason for drawing the line where it is, it is increasingly arbitrary, and less and less useful for any clinical decision making. Current treatment guidelines use other CD4 levels and viral load levels to indicate optimal treatments and when to intervene. An AIDS diagnosis does still carry weight in many contexts, such as benefits, but may have the least importance in the clinical setting.
posted by gingerbeer at 7:45 AM on February 5, 2008

Learn something new every day. Thanks for the correction.
posted by jmd82 at 8:56 AM on February 5, 2008