The excellent summary of the 2003 recommendations of the International AIDS Society—USA panel on antiretroviral drug testing in adults did not mention the potential utility of resistance testing in guiding postexposure prophylaxis (PEP) following high-risk needlestick injury in health care workers .
The Centers for Disease Control and Prevention (Atlanta, GA) has received reports of 57 documented and 138 possible cases of HIV seroconversion associated with occupational exposure to HIV in the United States as of December 2001 . These numbers are based on voluntary reporting by institutions and thus may underestimate the frequency of nosocomial transmission of HIV.
Although there are no data from randomized controlled trials of PEP in this setting, a retrospective case-control study found an 81% reduction in the risk of HIV infection with postexposure treatment of health care workers with zidovudine . Data from clinical trials of prophylaxis against perinatal HIV transmission and from animal studies also support the effectiveness of PEP; these studies also suggest that PEP should be administered within the first 24–48 h after needlestick injury to be optimally effective [2, 4].
Unfortunately, postexposure treatment does not completely prevent HIV infection after occupational exposure. Twenty-one cases of HIV infection despite PEP have been reported in health care workers in the United States and elsewhere . Resistance to antiretroviral drugs may contribute to failure of prophylaxis. Resistant HIV strains have been transmitted to health care workers despite PEP with combination antiretroviral regimens [2, 4]. The recent summary  reported that the estimated prevalence of any drug-resistant virus in US adults under care during the first 3 years of antiretroviral therapy in 1 study was 78%. A study of occupational exposure conducted at US sites in 1998 and 1999 found that, in source patients, there was a 39% incidence of HIV mutations associated with resistance to reverse-transcriptase inhibitors and a 10% incidence of mutations associated with resistance to protease inhibitors . It has therefore been recommended that all information about the source patient's HIV infection, including results of viral resistance testing, be used to help select an appropriate PEP regimen .
Health care workers have a right to as safe a workplace environment as possible. Educational and engineering efforts aimed at reducing needlestick injuries are an important component of improving safety in the medical workplace. When high-risk needlestick injuries do occur, prompt administration of an optimal PEP antiretroviral regimen is essential. I believe it is important to have the results of a relatively recent antiretroviral drug resistance test available in each patient's chart to help select this optimal PEP therapy.