Understanding Your Labs Jordan E. Lake, MD, MSc AAHU August 15, 2013
Labs 101 “Why do you need to do so many blood tests!?!”
Labs 101: Three Questions • What labs do we draw? • What do these labs tell us? • How often do we need these labs?
T cells 101 • T cells are immune system cells that become infected by HIV when the virus recognizes proteins on the T cell surface • One of these proteins is called CD4 • When doctors and patients are talking, they may refer to T cells or CD4 cells (same thing)
T cells 101 • The number of T cells tells us how healthy our immune system is (normal ≈ >700 cells/mm3) • As our 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 are busy helping to fight infection and cancer (they are also called “helper” T cells) • As T cell number decreases and T cells become weaker, their ability to “help” goes down.
T cells 101 Starting effective HIV medicines • stops the HIV virus from making new virus (replicating) • stops T cells from dying • allows your body the chance to make new cells Makes your T cells go up
T cells 101 What does the number of T cells tell me • <200cells/mm3: AIDS-related disease “danger zone” • 200-349cells/mm3: not in danger zone, but immune system still weak, certain infections more common • 350-499cells/mm3: getting stronger • ≥500cells/mm3: Ideal
HIV Viral Load 101 • Viral load (VL) is the amount of HIV in the body • Without HIV medicines, VL is high • With effective HIV medicines, no new HIV viruses are made, and the VL goes down
HIV Viral Load 101 Q: What is “undetectable”? A: Undetectable means that there is less HIV in your blood than the test can detect, NOT that there isn’t any virus in your body Note: The virus lives in many places in your body other than your blood.
HIV Genotype 101 • Genotypes tell us what medications the HIV virus in our body is sensitive to • It is specific for each individual patient, and helps doctors choose a medication regimen they feel confident will work • Also called a “resistance test”
When To Check Labs • T cell count: at diagnosis, then every 3-6 months • 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