Plasma Derived Factor Concentrate
Several methods are used to get rid of viruses and unwanted proteins in factor made from plasma. Some makers of factor use more than one method. Read the package insert or ask your doctor to find out how the factor you use is treated. The most common methods are:
- Heat treatment – the factor is heated either with dry heat or under pressurized steam.
- Microfiltration – the factor is put through a very fine filter to remove viruses.
- Monoclonal antibody chromatography – this process separates the factor from everything else in the plasma.
- Pasteurization – the factor is mixed in a liquid and then heated.
- Solvent/detergent – the plasma is mixed with two chemicals, a solvent and a detergent. The chemicals dissolve the coating around some viruses and kill them. A chemical, sodium thiocyanate, is sometimes used to kill viruses.
Some viruses resist these methods. People have gotten Hepatitis A from factor that was treated with solvent/detergent. Parvovirus B19 is not killed by solvent/detergent or pasteurization. It causes a mild illness in children called “fifth disease.” If a pregnant woman gets parvovirus B19, it can be very dangerous for her baby. It is also a dangerous virus for people whose immune systems do not work well or for people who are anemic (have low red blood cell counts). The National Bleeding Disorders Foundation (NBDF) has asked the government to screen blood for parvovirus B19. Scientists are also working on a vaccine (shot) to protect against parvovirus.
There may be other germs in human blood that we don’t know about. If so, they could show up in factor made from plasma. Fortunately, the methods used now to treat plasma-derived factor seem to be effective in preventing infections.
For children in the United States who need factor concentrate containing VWF, plasma-derived products are their only option. For adults, a recombinant factor concentrate is also available to use in certain situations.