A red line and a black line on the HIV test paper indicates that the test result is invalid, and under normal circumstances the test result will not have a black line. HIV test paper, also known as AIDS test paper, test paper on the C area is the quality control area, the T area is the detection area, after the test of the C area appears a red line indicates that it is negative, the specimen involved in the test does not contain AIDS-specific antibodies, the patient has a high probability of not being infected with AIDS. The presence of a red line in each of the C and T zones indicates a positive result, which means that the tested specimen may contain AIDS-specific antibodies, indicating that the patient has a higher chance of being infected with AIDS, but it is also necessary to go for further examination. The above two test results are normal phenomena; a red line and a black line on the HIV test paper means that the test result is invalid, and the black line on the test may be the result of contamination of the test paper, or the test paper has passed the expiration date, which has no diagnostic significance. If you use HIV test strips correctly, the test results will be more accurate.