Reliabilty of Two Orasure Home Test

[whatsup2]

Doctors, I would appreciate one of you answering the following questions.

I have an earlier thread where I explained I two protected incidents over 16 months ago.  I took the new Orasure Saliva test in Dec, 2012 and it was negative. ( over 16 months after last incident).

After I took that test, I read that the new Orasure at home access test has a sensativity of onlty 91.7 % and gives a false negative 1 out of 12 times. So I was concerned that perhaps I obtained a false negative.  Last week I took another Orasure Home Access Saliva test. It was negative as well. This test was bought at a different drug store than one in December.


From a medical (statistics, or other math ) perspective how much does the second negative test increase the liklihood that my result is truly negative and I dont have false negati ve. Pehaps the other way  is to ask what is the liklihood of both being false negative.  I assume with two negative results that is , from a statistic standpoint much more certain.

I assume with the new Orasure test on the market these type questions may come up more often,

Thank you

[Edward W Hook, MD]

Gald to help. Take care and please don't worry.  EWH

[whatsup2]

Thank you.

[Edward W Hook, MD]

Sorry, I misseed/forgot that a condom was used.  That makes the risk even lower and makes whther or not she was an IV drug user virtually irrelavant.  Time to believe your test results and put these concerns behind you. EWH

[whatsup2]

Thank you for your comment, One final question. I do not know if either female was an IV drug user. Probably not .But if that factor is unknown, what is the risk of transmission from each incident  since a condom was used with each incident.

Again thank you.

[Edward W Hook, MD]

Welcome back to the Forum. I'm sorry that you continue to worry about the two low risk exposures that you mentioned in your December questions.  I'll try to address your continuing concerns using a slightly different approach than Dr. Handsfield did to get to the same place.  In the U.S. the likelihood of a heterosexual woman who is not an IV drug user having HIV is less than 1 infection per 10,000 women and the risk for female to male transmission of infection from a single episode of unprotected intercourse is less than 1 infection per 1000 acts of intercourse.  Putting these two figures together, before testing your risk for infection for each single episode of intercourse is less than 1 in 10 million.  Thus even before testing the odds are very much in your favor of not having acquired HIV.  Then with testing you make those odds lower still.

HIV tests are among the most reliable tests available in medicine and the oral tests are considered for approval using the same criteria as the tests which are performed on blood.  There is no lower or weaker criterion for either saliva tests or for home tests, as long as they are done properly.  that you got the same result twice suggests that you are doing the tests properly (other studies have shown that the average 8th grader can perform them accurately and correctly).

Thus, putting all these facts together, you should now be completely confident that you did not get HIV.  Your repeat testing makes it less likely that your initial test was falsely negative but not much less so becasue the risk was so very low to start with.  Further testing really is not necessary and would be a waste of your time and resources.  

I hope these comments are helpful. EWH