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HIV Viral Load Testing

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The HIV viral load is the number of copies of the human immunodeficiency virus in your blood and other parts of your body. The HIV viral load test involves taking a blood sample from a vein in your arm. The amount of HIV in your blood is then measured. Along with other tests, the HIV viral load test helps monitor your disease, guide HIV therapy, and predict how your disease may progress. Keeping your viral load low can reduce complications of HIV disease and extend your life.

Two common test numbers you will want to know are your viral load and your CD4 count. Because the viral load measures the amount of virus in your body, you want a low viral load number. The CD4 or Tcell number, measures the strength or your immune system, thus you want a high CD4 or Tcell number.

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When to Have an HIV Viral Load Test

The different times you need an HIV viral load test include:

  • Right after diagnosis. This gives what's called a baseline measurement. Future results can be compared to it.
  • Every two to eight weeks at the start of treatment or with a change in treatment. This helps to evaluate how well medication is working.
  • Every three to six months or as your doctor directs if treatment is effective

 

How HIV Viral Load Is Measured

There are several different methods for measuring your HIV viral load. It is best to stay with the same method each time because different tests can produce slightly different results. New, more sensitive methods are constantly being developed. These are the three common tests currently used to detect HIV viral load. All work well.

PCR (polymerase chain reaction) uses an enzyme to multiply the HIV RNA in the blood sample. (RNA is the part of HIV that knows how to make copies of the virus.) This makes it easier to measure the amount of HIV RNA in the blood sample. A new ultrasensitive PCR test can measure down to 20 copies of HIV RNA. This is the most common test used.

bDNA (branched-chain DNA) creates a light signal whose brightness depends on the amount of viral RNA present.

NASBA (nucleic acid sequence based amplification) amplifies the viral proteins, making HIV viral load easier to measure.

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