28 days is long enough for a conclusive test so your 54 works for you.We rely on the opinion of expert doctors and some use theoretical risks so use unnecessarilly conservative timelines.
dont use symptoms to diagnose hiv
CDC itself says in one of the recent publications on HIV testing that 4th generation test is accurate 3-4 weeks earlier than its predessor 3rd generation test. If we take only this statement alone, 4th generation test should be conclusive at 8-9 weeks time.
CDC will issue its revised guidelines sooner or later, however they have their own work protocol.
Many experts on HIV around the globe believe that this test is highly sensitive and very accurate even before the formation of antibodies due to its capability of detecting p24, a protien attached to core of the virus. Very rare seronegative cases are also possible now to pick up, earlier tests were unable to pick and reporting false negative.
A negative result may be taken correct with confidence if done post 28 days of the exposure.