Condoms were tested in an in vitro system simulating key physical conditions that can influence viral particle leakage through condoms during actual coitus. The system quantitatively addresses pressure, pH, temperature, surfactant properties, and anatomical geometry. A suspension of fluorescence-labeled, 110-nm polystyrene microspheres models free human immunodeficiency virus (HIV) in semen, and condom leakage is detected spectrofluorometrically. Leakage of HIV-sized particles through latex condoms was detectable (P less than 0.03) for as many as 29 of the 89 condoms tested. Worst-case condom barrier effectiveness (fluid transfer prevention), however, is shown to be at least 10(4) times better than not using a condom at all, suggesting that condom use substantially reduces but does not eliminate the risk of HIV transmission.
PIP: Physical science researchers tested the ability of 89 undamaged latex condoms manufactured in the US to prevent passage of HIV=size particles under simulated physiologic conditions at their Food and Drug Administration laboratory in Rockville, Maryland. The design of the test system considered particle size, pH, surface tension, and time. A suspension of polystyrene 110 nm microspheres labeled with fluorescent dye served as the HIV-sized particle model in semen. They challenged each condom with this suspension for 30 minutes. The test did not include motion since stretching over the penis accounts for most pore stretching. Leakage of fluorescent dye occurred in 29 condoms (p .03). 21 condoms leaked at minimum leak rates 1 nl/s, 7 at 1-6 nl/s, and 1 at around 10 nl/s. Assuming the leakage occurred through the only pore in each condom, the pore diameters ranged from 2 to 7 mcm. Also assuming an even more conservative criterion, the qualitative results were the same: 11 condoms with leak rates were nl/s vs. 6 condoms with leak rates 1-9 nl/s (p .002). The widely used 300 ml water test did not indicate any pores in any of the condoms. In the extreme and highly unlikely scenario of all the fluid being pumped out of the condom, the transfer rate would be about 0.1 mcl after 10 minutes of thrusting after ejaculation filled the condom with semen (i.e., 0.01% of a typical 3 ml ejaculate). Thus proper use of latex condoms would result in exposure reduction from HIV of at least 4 orders of magnitude. These findings demonstrated that use of latex condoms can significantly reduce the risk of HIV transmission, but it does not eliminate that risk.