Detection of HIV Antibody and Antigen (p24) in Residual Blood on Needles and Glass

There is a significant rate of percutaneous injury with needles during the care of patients with acquired immunodeficiency syndrome (AIDS). Following puncture injury, it is recommended that the source of the contaminating blood be checked, and if human immunodeficiency virus-type 1- (HIV-1)-seropositive, zidovudine prophylaxis be considered. As the source of contaminating blood may be unknown, we studied the detectability of HIV-1 antibody and circulating antigen (p24) in the residual blood from needles and pieces of glass at various intervals following exposure to blood. The residual volume of blood remaining in needles varied from 183 ±50 μ 1 for a 20 G needle to 7.8 ± 1 μ 1 for a 27 G needle, and the residual blood on small pieces of glass varied from 23 μ 1 for a piece weighing 558 mg to 2 μ 1 for a piece weighing 21 mg. Analysis of washed samples of residual blood from all 20 G through 26 G needles and from broken pieces of glass larger than 0.41 g that had been exposed to HIV-1-seropositive blood and left at room temperature for one hour, one day and one week resulted in positive tests for HIV-1 antibody by enzyme-linked immunosorbent assay (ELISA), immunofluorescence and Western blot assays. The circulating antigen was detected in residual blood of 20 G through 26 G needles, but not from contaminated pieces of glass. This technique could be applied to situations where a healthcare worker pricked him- or herself with a needle or with a piece of glass that had been contaminated with blood of unknown seroreactivity. If HIV-1 ELISA, immunofluorescence, Western blot and circulating antigen assays are negative, the individual can be reassured. Because only 0.4% of needlestick injuries with HIV-1-seropositive blood have resulted in seroconversion, there must be other factors, as yet unknown, that predispose to infection.