HIV in Blood

[thinkofme33]

Dear Dr.

I really appreciate the great work you do here and are very knowledgeable in terms of hiv and that is why i want to ask a question which has always bothered me but never bother asking as i felt it would have been thought of as a stupid question.

I know this rarely happens but again it has happened i believe in Nevada and by a dentist which infected his patients.  I went for a hiv blood test and i was not sure if the needle used was brand new, it was placed into vacutainer i was poked in vein for blood and a sucking tube was then attached to pull my blood.  If in the rare case the needle was used to draw blood from a HIV positive patient before me.

1.  Can i get infected?
2.  Even if there was hiv blood in the needle hollow it would not have gotten into my blood stream due to my blood being pulled rather then a fluid being injected into my veins?
3.  Would blood if left in the hollow part of needle and i was then injected to draw blood would automatically stream down into my bood stream or does it stay tightly in the hollow part until pushed out with a fluid?
4.  If there was HIV blood in the hollow part of the needle and my blood was drawn and it got sucked into the blood collection tube along with my blood which was hiv negative, during lab testing would the test be reactive?
5.  What happens when HIV negative blood is mixed with another persons hiv positive blood and the then the sample tested?
6.  How accurate is HIV lab testing  (HIV 1/2 Screen MEIA) in Canada to detect HIV, 3 weeks following exposure percentage wise?

I hope you can please answer my question i am just very paranoid and this will really help me in the future.

Thanks.

[Edward W Hook, MD]

Welcome to our Forum.  We receive questions similar to yours and before I address our specific questions, let me reassure you that in North America there is virtually no risk of HIV from having your blood drawn.  The case that I believe you are referring to did not involve blood drawing but rather the re-use of medication vials on multiple patients in which the contents of the vial was contaminated with blood, then material in the vial was injected back into other persons.  For the reasons you imply in your questions, there is virtually no risk even if someone were to re-use blood drawing needles since the direction of blood flow is outward (from the body) rather than inward.  Thus, to worry about such an exposure is scientifically unfounded.  Now, to address your specific concerns:

1.  See above, no. furthermore, I would add that most material now used for blood drawing with vacutainers (the vacuum blood tubes) is designed so that they cannot be re-used, even accidentally.  
2.  Correct.  As I said above, the blood would be flowing outward, not inward and therefore would not put you at risk.
3.  No, it would not go into your arm.  the vacuum would take it in the opposite direction.
4.  Yes, this sort of contamination could, theoretically, turn a blood test positive.
5.  This is the same as the question no. 4 above.  Same answer
6.  At 3 weeks a blood test would detect about 2/3 to 75% of infections which occurred 3 weeks earlier.  At 4 weeks it would detect over 90% and at 8 weeks virtually all infections would be detectable.

Hope these answers are helpful. you really do not need to worry about having your blood drawn.  EWH

[thinkofme33]

Thanks Dr, that was very helpful. You guys are great as always!!!