Rapid Diagnostic Testing for HIV:
Clinical Implications of a New Diagnostic Tool

RECOMMENDATIONS FOR RAPID HIV TESTING
FOLLOWING POTENTIAL OCCUPATIONAL HIV EXPOSURE

Transmission of blood-borne pathogens is an occupational hazard for health care workers. The average risk of HIV infection from all types of percutaneous exposures to HIV-infected blood is approximately 0.3 percent. A CDC case control study showed that the risk of HIV-infection exceeded 0.3 percent for exposures that involved a deep injury to the health care worker; visible blood on the device that caused the injury; a device that had been placed in the source patient's vascular system, (e.g., a needle used for phlebotomy); or a source-patient who died as a result of AIDS within 60 days post-exposure.¹⁸

The average risk of HIV infection following a mucous membrane or skin exposure is less than the risk associated with a percutaneous exposure. After a mucous membrane exposure the average risk of HIV infection is 0.09 percent. The average risk of HIV infection after a skin exposure is less than 0.09 percent. The risk for skin exposure may be increased if skin contact is prolonged, if contact involved an extensive area of the skin, if the integrity of the skin is not intact, or if the exposure involves a higher titer of HIV.¹⁸

Following a high-risk occupational exposure, employers need to provide health care workers with a system for prompt evaluation, counseling, and follow-up. First aid needs to be administered immediately after an exposure. Puncture wounds and other cut injuries should be washed with soap and water. If oral and/or nasal mucosa has been exposed, they should be decontaminated by flushing with water. Eyes should be irrigated with clean water and saline or sterile irrigants that are designed for flushing eyes. The exposure should be reported to the person or department (e.g., employee health, infection control) responsible for managing exposures.¹⁹

The key to reducing the risk of occupational HIV transmission is to provide post-exposure prophylaxis as soon as possible following a potential exposure. Testing to determine the HIV status of the source of the exposure should be conducted as soon as possible after the incident. The exposure source should receive pre and post-test counseling and give consent for HIV testing. A rapid HIV-antibody test kit approved for use in the jurisdiction should be considered particularly if testing by EIA cannot be completed in 24-48 hours. Positive results by EIA or rapid HIV-antibody tests are considered to be highly suggestive of infection, whereas a negative result is an excellent indicator of the absence of HIV antibody. Confirmation of a reactive result by Western blot or IFA is not necessary to make initial decisions regarding post-exposure management but they should be completed before informing the source person.^18,19

HIV antibody tests should be performed on the exposed employee immediately to establish a baseline and then periodically for at least six months post-exposure, e.g., 6 weeks, 12 weeks, and six months. HIV testing should be performed on any health care worker who has an illness compatible with an acute retroviral syndrome following an occupational exposure, regardless of the interval since the exposure. HIV antibody testing using enzyme immunoassay (EIA) should also be used to monitor for HIV seroconversion. The routine use of direct assays, e.g., HIV antigen EIA or polymerase chain reaction for HIV RNA, to detect infection in health care workers is generally not recommended. The reliability of HIV RNA testing to detect very early infection has not been determined and it is not FDA approved for this purpose. The employee should be counseled on precautions to prevent secondary transmission of HIV.¹⁸

If appropriate, CDC recommendations for post-exposure prophylaxis (PEP) with laboratory monitoring should be offered to the employee. Although animal studies suggest that PEP probably is substantially less effective when started more than 24-36 hours post-exposure, the interval after which no benefit is gained from PEP for humans is undefined. In humans, the interval within which PEP should be initiated for optimal efficacy is not known. Therefore, if appropriate for the exposure, PEP should be started even when the interval since exposure exceeds 36 hours. Initiating therapy after a longer interval (e.g., one-week) might be considered for exposures that represent an increased risk for transmission.²⁰