This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'Window period in HIV is defined as \nSelect and explain. \nA. Period between onset of infection  and clinically detectable level of antibodies, B. Period between infection and appearance  of symptoms, C. Time between HIV positivity to AIDS, D. CD4 count < 200', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Window period\xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0\n\nThe time period between primary infection and detection of antibodies is called window period.\nTraditional methods used in the diagnosis of HIV such as (ELISA and western blot) are based on the detection of these antibodies i.e., these tests become positive once the antibodies appear in the blood.\nHowever, the recent methods used in the diagnosis of HIV are based on the detection of virus or virus particles (not antibodies).\nVirus or the virus particles appear early in the blood than antibodies so the newer methods have considerably reduced the period between the infection and the diagnosis i.e., they have reduced the window period\n\nMethods of the detection \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 Window period\n\nAntibody detection (ELISA western blot)\xa0→ \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 22 days\np24 Antigen \xa0\xa0→ \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa016 days\nNucleic\xa0detection\xa0→ \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 \xa0 12 days', 'role': 'assistant'}]