Your blood tests

The blood tests are the most important part of your medical supervision. Beside any health problems you might have, the blood tests are what your internist considers most when it comes to advising you when to start withbloedtest medications. If you already use medications, your blood tests will tell you:

  • if your pills are effectively suppressing your virus;
  • if your pills are causing side effects that you have not noticed yourself;
  • if you need to switch to other pills.

Normally you have blood tests done once every three to six months. That means that you will go to the blood lab in hospital to have your blood drawn. Some people with HIV get tested two or three weeks before their consultation, so that they can hear the results during the consultation. Others find it more practical to go hospital just one time. They will hear their results later by telephone or by e-mail, or they will get the result the next time they have an appointment in hospital.

In the blood lab
Between four and ten little vials of your blood will be drawn in the blood lab. That may sound like a lot, but it only amounts to half a teacup in total. The forms that you will fill in and give to the staff of the blood lab will tell them that you have HIV. Most of the nurses who work in the blood lab know all about HIV and always take special care since they know that any of the patients they draw blood from could have HIV (or, Hepatitis). Once in a while, there might be someone on the staff who is not comfortable doing that. The blood tests evaluate dozens of levels each time. Those enable your internist to monitor things like your cholesterol and the functioning of your liver and kidneys. Medications can also have negative effects, but the blood tests help you discover those in time.

What do the blood tests determine?
Your blood tests will usually determine your CD4-cell count and your viral load. Testing for resistance to medicines is only done just before you start taking HIV medications and in case you need switch to other medicines because your current medicines are not suppressing your HIV effectively. Determining your blood levels can only be done if you are using HIV medications. Even then, that is not done every time, but only when there is a reason for doing so.

CD4-cell count
The number of CD4 cells you have in your blood indicates how strong your immune system is. A CD4 cell (also known as a T4 cell) is a white blood cell. HIV makes copies of itself in CD4 cells and then destroys those cells. The higher the number of CD4 cells you have, the better your immune system works. If you do not have HIV and you are healthy, you will have between 500 and 1500 CD4 cells (per mm3 of blood). If you have fewer than 200 CD4 cells, you are much more likely to get infections. It is normal for the number of your CD4 cells to go up and down. If you are not yet using HIV medications it is likely that your CD4-cell count will drop after a while. Along with any symptoms you might have, your CD4-cell count is the most important thing your internist will consider when advising you about when to start using HIV medications. These days, most people with HIV start taking medicines when their CD4-cell count is between 350 and 500, but the ideas about the best time to start are changing as time goes on. Once you start using HIV medications, your CD4-cell count will most probably rise. Sometimes the number will increase within a couple of months, but sometimes it can take a couple of years.

Viral load
Your viral load is the amount of virus (that is to say the number of HIV virus particles) per millilitre of blood. In the months after you first get infected with HIV, your viral load is very high: often more than one million. Once your body starts making antibodies against HIV, your viral load will decrease. Like your CD4-cell count, your viral load can also go up and down. It does not mean so much if your viral load has gone up a lot since the last time you were tested. That could just be a normal swing. If your viral load is much higher again the next time you go for a blood test, then something is probably wrong. If you start using HIV medications, your viral load will probably drop within a couple of months until it is ‘undetectable’ (that is to say no longer measurable). That does not mean that you have been cured of HIV; that is still not possible. Some of the virus will remain in your body. If your viral load is undetectable, that means that you have fewer than 20 HIV virus particles per millilitre of blood (in some laboratories: fewer than 50). In that case, it is certain that that your HIV medications are suppressing your virus effectively. Your CD4-cell count will probably rise in the months after that too. If you continue to take your HIV medications according to the instructions, your viral load will remain undetectable. If your viral load becomes detectable (that is to say measurable) again, that could just be just an incident. If your viral load is still detectable after the next blood test, it could be that your virus is not longer being suppressed effectively. In that case, your internist will probably advise you to switch to other HIV medications.

Testing for resistance
HIV is a virus that makes sloppy copies of itself. Among all the sloppy copies, there can sometimes be one variation of the virus that is too smart for an HIV medication. This characteristic is known as resistance forming. This does not mean that an HIV medication will no longer work at all, and that you will suddenly be resistant to all HIV medications. Your HIV can be resistant to one particular medication or to all the HIV medications of a certain type. And it is not all or nothing: it could be that one medication does not work as well as others for you. How van you develop resistance?

  • You could be infected with a virus that was already resistant to a certain HIV medicine. That is the case for about one in ten people with HIV. In that case, you will have been infected by someone who is already using or has used medicines and who has a detectable viral load. It could also be that you were infected by someone who had not started using HIV medications yet, but that he or she got HIV from someone who was using medicines.
  • You can become resistant because you have not been careful enough in taking your HIV medications according to the instructions

If your virus is resistant, it is usually only resistant to one or a few HIV medications. That limits your treatment possibilities somewhat.

Testing for resistance will be done before you start taking HIV medications and if you switch to other HIV medications. That will determine in advance if  there are any HIV medications that will not work for your type of virus. If your viral load is undetectable, you cannot be tested for resistance since there will not be enough of the virus in your blood.

For one HIV medication (abacavir, an active ingredient used in Kivexa, Trizivir and Ziagen) it is possible to find out in advance, using a blood test, whether or not you are allergic for it. Another HIV medication (Celsentri) requires a blood test to be done in advance to determine if it will be effective against your type of virus

Testing for blood levels
To be able to suppress the virus effectively, enough of the active ingredients of the HIV medications has to be in your blood at any moment. For a number of the HIV medications (but also for many other medicines) it is possible to determine whether or not your blood contains the right amount of the active ingredient. If your blood level (that is to say the amount of that active ingredient in your blood) is too low, the medicine will not be effective enough and you will run the risk of becoming resistant to that medication. If your blood level is too high, you will run a greater risk of having side effects. Based on the results of the blood-level testing, the dose of a medication can be adjusted. Blood levels are tested if there is a reason for doing that, for example, if the virus is not being suppressed enough. Over the course of a day, your blood levels drop. By taking your HIV medicines on time, you can make sure that the blood level of those medications never drops too low.


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