Centers for Disease Control and Prevention. Case-control study of HIV seroconversion in health-care workers after percutaneous exposure to HIV-infected blood -- France, United Kingdom, and United States, January 1988-August 1994. JAMA 1996; 275:274-275.

Collaborating with French and British public health authorities, the CDC conducted a retrospective case-control study to determine factors that influence health care workers' risk for HIV infection after percutaneous blood exposure.

Based on their analysis of 31 case-HCWs and 679 control-HCWs, researchers found an increased risk for HIV infection following percutaneous exposure to HIV-infected blood was associated with three factors. First, risk increased if exposure involved a larger quantity of blood, indicated by: a device visibly contaminated with the source patient's blood, a procedure involving a needle placed directly in a vein or artery, and a deep injury.

Second, the risk increased for exposures to blood from source patients with terminal illness, probably reflecting the higher HIV titer in blood late in the course of AIDS or other factors, such as the presence of syncytia-inducing HIV strains.

Third, data analysis suggested that use of zidovudine (ZDV) postexposure may be protective for HCWs. (See related story in Hospital Employee Health, June 1995, pp. 79-81.) After controlling for other factors associated with HIV transmission risk, the model indicates that the risk of HIV infection among HCWs who used ZDV was reduced by approximately 79%. The researchers caution that "the limitations of the study design must be considered when interpreting these results," as a retrospective case-control study is not optimal for assessing ZDV efficacy.

Nevertheless, the researchers point out that this is the first study of HCWs exposed to HIV that assesses the effectiveness of ZDV as postexposure prophylaxis. The drug is not approved by the U.S. Food and Drug Administration for that purpose, and the Public Health Service (PHS) in 1990 concluded that a recommendation for or against its use could not be made because of limited knowledge of efficacy and toxicity. The PHS is evaluating this study and other information, which could lead to revised recommendations for managing occupational HIV exposure.

To assess potential risk factors for HIV infection following percutaneous exposure, researchers used data reported to national surveillance systems in the United States, the United Kingdom, and France. Case-HCWs had a documented occupational percutaneous exposure to HIV-infected blood, HIV seroconversion temporally associated with the exposure, and no other concurrent HIV exposure.

Control-HCWs had the same type of documented exposure and were HIV-seronegative at the time of exposure and at least six months later.

HCW information obtained included age, sex, occupation, work location, whether postexposure antiretroviral agents were offered, whether they were used, how long after the exposure the first dose occurred, daily dosage, and duration of treatment. Source patient data also were gathered.

Exposure information included type of device, gauge of hollow-bore needle, type of procedure being performed, whether the procedure was an emergency, use of gloves, time from use of device to exposure, presence of visible source patient's blood on the device, and injury severity (superficial, moderate, or deep).

Of the 31 exposures sustained by case-HCWs, 29 (94%) were needlesticks (all with hollow needles), and two (7%) involved other sharp objects. Of the 679 exposures sustained by control-HCWs, 620 (91%) were needlesticks (594 hollow and 26 solid needles) and 59 (9%) involved other sharp objects.

From 1990 to 1994, 17 (81%) of 21 case-HCWs had been offered ZDV; from September 1990 through 1994, 268 (79%) of 338 control-HCWs were offered ZDV. ZDV postexposure prophylaxis was used by nine (29%) case-HCWs and 247 (36%) control-HCWs. Case-HCWs were significantly less likely to use ZDV than control-HCWs.

All factors in the model also were significant when the analysis was restricted to case-HCWs from the United States.

[Editor's note: Single copies of the full report are available free until Dec. 21, 1996, from the CDC National AIDS Clearinghouse, P.O. Box 6003, Rockville, MD 20849-6003. Telephone: (800) 458-5231 or (301) 217-0023.] *