Question about testing results

[hansen]

Hello!

English is'nt my native tounge, hope you understand me anyway. Sorry for that in advance.

About 14 months after a low-risk situation, i took a rapid test. The test was  Alere Determine HIV-1/2 and was performed by the biggest hiv-organization in my country.

The result was negative and i got of course very reliefed.

However, i've started to worry again regarding risk of false negative tests.

Reading on aleres homepage, the technical specs of the tests says: Over-all 99.75% on specification. (100% on sensitivity).

1. Does this mean that 0,25% of all people (who actually are infected) beeing tested as negative, living their lives beeing sick but they dont know about it?

2. What makes this number 99,75% and not 100? the quality of the test it self? not enough anti bodies in blood? The Control stuff on the test worked fine and a very clear line appeard in that "window".

3. In 14 months, i guess EVERYONE has developed anti bodies enough to be detected?
 
4. If i understand this correct there should be a reason for everyone to take at least two tests? Please correct me, and please tell me i am wrong...

5. Also - did i get it correct. Specificity is false negative, Sensitivity tells about false postive?

Br,

Hansen

[Ptrk3]

False negatives are very rare.

No, the statistic does not mean that .25 percent of people testing "negative" are "positive."  It is a model.

Many experts recommend that testing for HIV antibodies be conducted six weeks after potential exposure, then at 13 weeks for confirmation of the six week results.

You tested negative 14 months after a "low risk" activity.  There is no reason whatsoever for you to believe your test was falsely negative.

If you can't accept that fact, get another test and move on with your life.

[hansen]

Thanks for your answer!

All of you moderators are doing a great job! Heros actually!

Just a final question, you state that it is very rare with false negatives.

More rare than 0.25% of all the negative tests i take it then?

Br, Hansen

[Ptrk3]

You can read for yourself:

http://i-base.info/qa/factsheets/hiv-transmission-and-testing

From the link:

What is a ‘false negative’ test result?

A false negative test result occurs when the test shows negative and the person is really HIV positive.

This is very rare. It usually occurs during the window period when someone is very recently infected but the test can’t pick up the infection.

Nearly all tests have a margin of error. this is usually small. With HIV antibody tests only 0.3% of tests (3 tests in every 1000) will be a false negative after 3 months.

With fourth generation tests, it is lower still at 3 months.

If you are worried you can take a second test. This will eliminate the possibility of a false negative result.