A CASE-CONTROL STUDY OF HIV SEROCONVERSION IN HEALTH-CARE WORKERS AFTER PERCUTANEOUS EXPOSURE

Background The average risk of human immunodeficiency virus (HIV) infe ction after percutaneous exposure to HIV-infected blood is 0.3 percent , but the factors that influence this risk are not well understood. Me thods We conducted a case-control study Of health care workers with oc cupational, percutaneous exposure to HIV-infected blood. The case pati ents were those who became seropositive after exposure to HIV, as repo rted by national surveillance systems in France, Italy, the United Kin gdom, and the United States. The controls were health care workers in a prospective surveillance project who were exposed to HIV but did not seroconvert. Results Logistic-regression analysis based on 33 case pa tients and 665 controls showed that significant risk factors for seroc onversion were deep injury (odds ratio=15; 95 percent confidence inter val, 6.0 to 41), injury with a device that was visibly contaminated wi th the source patient's blood (odds ratio=6.2; 95 percent confidence i nterval, 2.2 to 21), a procedure involving a needle placed in the sour ce patient's artery or vein (odds ratio=4.3; 95 percent confidence int erval, 1.7 to 12), and exposure to a source patient who died of the ac quired immunodeficiency syndrome within two months afterward (odds rat io=5.6; 95 percent confidence interval, 2.0 to 16). The case patients were significantly less likely than the controls to have taken zidovud ine after the exposure (odds ratio=0.19; 95 percent confidence interva l, 0.06 to 0.52). Conclusions The risk of HIV infection after percutan eous exposure increases with a larger volume of blood and, probably, a higher titer of HIV in the source patient's blood. Postexposure proph ylaxis with zidovudine appears to be protective. (C) 1997, Massachuset ts Medical Society.