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Understanding HIV-Related Lab Tests Jordan E. Lake, MD, MSc

AAHU August 27, 2014

+Labs 101

“Why do you need to take so much blood!?!”

+Labs 101: Three Questions

What labs do we draw?

What do these labs tell us?

How often do we need these labs?

+ T cells 101T cell: a type of immune system cell

T cells become infected by HIV when the virus recognizes proteins on the T cell surface

One of these proteins is called CD4

Doctors and patients may talk about T cells or CD4 cells (same thing)

+T cells 101

The number of T cells tells us how healthy the immune system is (normal ≥700 cells/mm3)

As the immune system becomes weaker from HIV, the number of T cells goes down (they die and your body can’t make more)

+T cells 101

When T cells are not infected with HIV, they help to fight infection and cancer

As T cell number decreases and T cells become weaker, their ability to “help” goes down

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http://www.southsudanmedicaljournal.com/archive/2009-08/untitled-resource.html

+T cells 101

What does the number of T cells tell me?

<200cells/mm3: AIDS, immune system very weak

200-349cells/mm3: immune system still weak, some infections more common

350-499cells/mm3: immune system is getting stronger

≥500cells/mm3: Ideal

+HIV Viral Load 101

Viral load (VL) is the amount of HIV in the blood in copies/mL

Without HIV medicines, VL is high

With effective HIV medicines, no new HIV viruses are made, and the VL goes down

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+HIV Viral Load 101

Q: What does “undetectable” mean?

A: Undetectable means there is less HIV in the blood than the test can detect, NOT that the virus is gone from the body

-The virus lives in many places in the body other than your blood

-Cells in the blood can be infected with HIV but not release virus into the blood

+Where is the HIV Virus in the Body?

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How Do HIV Medications Affect T cells and the HIV Viral Load?

+Effective HIV Medicines

Stops new HIV virus from being made

Stops T cells from dying

Allows the body the chance to make new T cells

atripla.com

+HIV Genotype 101

The genotype tells us what medications the HIV virus is sensitive to

It is specific to each person, and helps doctors choose medication regimens

Also called a “resistance test”

+HIV Genotype 101

+When To Check Labs

T cell count: at diagnosis, then every 3-6 months

HIV Viral Load: at diagnosis, 4 weeks after starting HIV medicines, 12 weeks after starting medicines, then 2-3 times per year

Genotype: at diagnosis, if VL going up on medicines and resistance suspected

+Other Labs We Check

Kidneys: blood creatinine, urinalysis

Liver: AST, ALT, bilirubin

Anemia: hemoglobin

Immune system: white and red blood cell counts and characteristics

Cholesterol: lipid panel

STIs: RPR, Gonorrhea/Chlamydia as appropriate for individual patient

Viral hepatitis: Hepatitis A,B, and C at diagnosis, Hepatitis B and C if liver abnormalities, plus Hepatitis C antibody yearly for MSM

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