test generation

[SaferSexFan]

Why do I see questions that mention the generation level of a test? What does that mean? SHould i be concerned if my tests arent of a particular generation?

Thanks

[ECN44120]

No concern, the generation diferentiaites how the test work but for all test a 3 month negative is conclusive and a positive would need a western blot or IFA confirmation test

[SaferSexFan]

and is 6 weeks -- 8 weeks also conclusive? even for older?

[ECN44120]

No test is conclusive before 3 months but all test would be 95% accurate at 6 weeks and 98% accurate at 8 weeks

[Frank303]

Years ago they changed the type of reagents in test kit, which moved HIV testing forward significantly by reducing the window period.
Subsequent generations have not reduced the windoe pwriod by so much.

The 4th generation kits as well as checking for antibodies check for antigen too which is present early on for a couple of weeks, I think day 16 to about 3rd week of initial infection.  

There is a transit period (a second window period) between unbound antigen being detectable and unbound antibodies being detectable as antibodies bind to antigen and they theoretically cancel each other out during the transit period.
There are some reports in the medical lierature of 4th generation tests not being as sensitive on antibody detection as 3rd generaton tests.
  
I don't think there are many of the older generation kits in circulation.
The reagent strips ar eupdated all the time so don't concern yourself twith that.  

[ECN44120]

Here is a link with a graph that explain what Frank just acurratly said.

http://www.roche-hiv.com/portal/eipf/pb/hiv/Roche-HIV/first-line_diagnosis;jsessionid=H9P788Z1313xnxbdN0R26vvG5rthpHfcbcQCw2BhxS0wJMx2Zb2B!-1520863363_DARGS=/portal/templates/rochehiv/page/html/searchInPageTemplate.jsp