What is the normal value for combined HIV antigen and antibody testing?

HIV antigen and antibody combination test has a normal reference value of less than 1.0 S/CO, indicating that neither HIV antigen nor antibody is detected in the sample, which is considered a negative result. A value greater than or equal to 1.0 S/CO is considered positive or in the "gray zone," requiring further confirmation. If there has been high-risk behavior or abnormal test results, prompt medical consultation is recommended.

This test simultaneously detects HIV p24 antigen and antibodies, shortening the detection window period after infection and enabling earlier identification of infection compared to antibody-only testing. Normally, individuals not infected with HIV do not have related antigens or antibodies in their bodies, so test values remain below the cutoff threshold of 1.0 S/CO, suggesting either no infection or presence within the window period.

It should be noted that the testing window period is approximately 2–4 weeks, during which false-negative results may occur. If the test result falls near the cutoff value (i.e., in the gray zone), it could indicate early-stage infection, testing error, or nonspecific reactions; retesting or confirmatory testing is needed to clarify the outcome.

Prior to testing, avoid alcohol consumption and staying up late to ensure stable physical condition. After testing, maintain a calm mindset and avoid excessive anxiety. Following high-risk exposure, follow-up tests should be conducted at recommended intervals. Practice preventive measures in daily life, such as avoiding unprotected sex and sharing of needles, to reduce the risk of infection.