plasma vs serum VL


I have asked a question regarding if there is any difference in the amount of hiv found in serum or plasma vs. whole blood when working in the laboratory. I have been told that when it is spun down, the virus is pulled to the bottom of the tube in the whole blood, is this true? And also, how long will hiv survive in an open vile of blood when the cap is removed?


I see that you have asked this question to several experts and through various forums. I will attempt to answer all the questions you have submitted.

Yes, there is a difference between serum and plasma HIV viral load (VL). The HIV VL in serum is about 10-20% lower than plasma if you drew blood from the same patient at the same time.

Regarding your question about what happens when you centrifuge, well that is more tricky to answer as it depends on how fast and how long you centrifuge the specimen. So if you were able to centrifuge it fast enough for a long time ( 100,000 xg for 15 minutes or 25,000 xg for an hour), the concentration of the VL in the lower part of the tube would be higher than the upper part of the tube WHILE IT IS SPINNING. If the centrifuge is going slower, it may take hours to pellet the virus.

One of your other questions asked about semen or it may have been a typo. Either way, the concentration in the semen may not be the same as in blood. There is not a direct correlation.

There have been several studies looking at HIV survival and for the most part , HIV dies relatively quickly outside the body in regards to risk of transmission. How long it will actually live inside a tube of blood, I really do not know.

I am not sure why you are asking about the differences in VL in spun specimens and if you are trying to figure out relative risks of HIV transmission in the laboratory, I would suggest that you contact a local retrovirology lab for further information. The bottom line is that HIV can be transmitted via blood contact in the laboratory and you should be practicing "universal precautions" with all body fluids. I would not try to go by relative risks of whether it is plasma, serum , spun or unspun. Precaution should be used with all specimens and treated equally as potentially transmissable.