HCWs seroconvert to HIV despite drug therapy
March 1, 2000 3 minutes read
HCWs seroconvert to HIV despite drug therapy
Jochimsen EM, Luo CC, Beltrami JF, et al. Investigations of possible failures of postexposure prophylaxis following occupational exposures to Human Immunodeficiency Virus. Arch Intern Med 1999; 159:2,361-2,363.
Why does postexposure prophylaxis fail in some cases to prevent seroconversion after occupational exposure to HIV? Researchers at the Centers for Disease Control and Prevention in Atlanta are exploring that question through case studies. This article discusses two such case studies, in which health care workers seroconverted to HIV after needlestick injuries despite PEP with combination drug therapy.
The researchers begin by noting that guidelines call for the use of combination drug therapy, including zidovudine, as chemoprophylaxis after certain occupational exposures to HIV. "Since little is known about the effectiveness of PEP for occupational HIV exposures, investigation of cases of possible failure can provide important information about factors that may influence PEP efficacy and occupational HIV transmission," the authors state.
In the first case, a health care worker received three cuts to the thumb from a broken blood collection tube containing the blood of an HIV-infected patient. The exposure involved a deep injury and a large volume of source blood, leading to a high risk of HIV transmission. The source patient was being treated with antiviral agents, raising the possibility that the patient had drug-resistant HIV.
The health care worker received PEP with zidovudine, lamivudine, and indinavir within 30 minutes. A baseline HIV test the next day was negative. However, within eight days, the health care worker had an "acute, viral-like illness," and within 17 days, tested positive for HIV.
However, further investigation showed that the health care worker had another possible risk factor for HIV infection and took no more than one dose of the PEP regimen. The two "alleged" HCW virus samples didn’t match each other (that is, they came from different individuals) and also did not match the source patient. Researchers concluded that this did not represent a failure of PEP.
In the second case, a health care worker was splashed in the face with serum from an HIV-infected patient. The HCW had had a facial dermabrasion procedure the day before, and the source was being treated with combination therapy.
The HCW began PEP with zidovudine, lami vu dine, and indinavir within six and a half hours of exposure. Although tests at baseline and at six weeks were negative, tests at one month were positive. A follow-up at 12 weeks produced positive test results, despite six weeks of PEP. Analysis showed the one-month and three-month samples did not match each other. The CDC obtained a blood specimen directly from the HCW and compared it to blood from the source patient and found they were not genetically related.
"We have concluded that the HCW did not seroconvert to HIV from the reported occupational exposure but that the seroconversion occurred sometime between six and 12 weeks after that exposure," the authors state. "The source of the HCW’s HIV infection remains unclear, although a follow-up interview with the HCW revealed a possible nonoccupational exposure to HIV."
The authors stress the importance of epidemiologic and laboratory investigations following reports of possible PEP failure. In both cases, blood samples thought to come from one person actually were from different individuals, a situation that could occur due to lab error or deliberate substitution.
"The outcome of a PEP failure investigation should not affect the management of the infected HCW or change the institution’s infection control policies for managing occupational exposures to HIV," the authors state. Hospital employee health practitioners can receive assistance with such investigations from the CDC by calling (404) 639-6425.
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