The real meaning of undetectable (UNDETECTABLE VIRAL LOAD, 2010)


Hi Dr. Hope you had an excellent 2009 and I pray for you that 2010 will be full of good health. Hope you can answer my question. Does undetectable Viral Load & VL <20cp/ml refers to the same thing? What is the difference? If there is no difference, then why the same lab is reporting the result in two different ways? Thank you so much for your kindness.



Undetectable means the HIV plasma viral load is below the lower limit of detection for the particular test assay that is being used. Early viral load tests could only test down to 10,000 copies. Newer tests were able to test down to 500 copies of the virus per milliliter of plasma. The even newer ultrasensitive viral load assays can test all the way down to 25 or 50 copies/ml. We now have ultra-ultrasensitive assays available in some research laboratories that can test down to a single copy per ml! However, even in HIV-positive patients with HIV plasma viral loads below 1 copy/ml, this does not mean they have zero virus in their body. HIV still exists inside cells in the blood, lymph nodes and other body compartments.

In your case, "undetectable" and VL < 20 cp/ml (viral load less than 20 copies per ml) means you have an "undetectable" HIV plasma viral load and the lower limit of detection for the assay used was 20 copies per milliliter. Your blood has fewer copies than the lowest number detected by this test. So it's less than 20 copies per milliliter. I hope that helps clear up any confusion.

While we are on the topic of "undetectable" viral loads, I should take the opportunity to clear up common misunderstandings about this terminology:

  1. Undetectable does not mean cured! There is no cure for HIV/AIDS (yet).

  2. Undetectable does not mean noninfectious (that you cannot transmit the virus to others)! We have cases documenting HIV transmission from a man with an undetectable viral load to his HIV-negative wife via unprotected vaginal sex. There are also cases of mother-to-child transmission, despite the mother having an undetectable viral load.

  1. Undetectable does not mean the virus cannot be detected anywhere in the body. Despite having an undetectable viral load in the blood (plasma), the virus would still be readily detectable in other tissues and body compartments.

  2. Effective combination antiretroviral therapy does not kill the virus! Rather it merely suppresses viral replication. Consequently, if someone with an undetectable viral load on combination antiretroviral therapy stops taking his drugs, the virus will soon start reproducing again and the viral load will skyrocket to levels near to where the viral load was before treatment was begun.

Be well. Stay well. Happy 2010!

Dr. Bob