Abstract: Because of immune system collapse, AIDS patients in late stage usually have insufficient or no antibody production (serological negative AIDS), resulting in failure of conventional diagnosis based on antibody detection and missed diagnosis or delayed diagnosis. This is called the the blind spot in clinical AIDS diagnosis. For the antibody screening positive cases, the cases with uncertain confirmation test results and the cases with late opportunistic infections or complications, it is essential to conduct timely nucleic acid detection based on epidemiological history, clinical symptoms and CD₄⁺T lymphocyte count to avoid missed diagnosis and misdiagnosis in AIDS diagnosis in late stage. Nucleic acid detection is recommended as the preferred diagnostic technique and method in National Technical Specifications for HIV/AIDS Testing (Revised Edition 2025) to facilitate the detection and diagnosis of AIDS in late stage.