My doctor has recommended western blot for HIV-1 and HIV-2 as a screening test. The RIBA test was negative for HIV, after 16 weeks of exposure. I also had a negative CMIA test, after 12 weeks post exposure. Hepatitis and STD panel are also negative. Is a negative western blot 100 % accurate and reliable at 16 weeks post-exposure? If western blot is so accurate, why it is not used as a screening test? Is a six months retest required despite a negative western blot at 16 weeks? Which generation is RIBA, and how accurate it is as a stand-alone screening test? Will a recent CMV affect these test results accuracy?