Needlesticks and hepatitis C

Charles John Palenik, MS, PhD

Hepatitis C virus (HCV) infection is the most common chronic bloodborne disease in the United States. Behavioral changes, greater implementation of standard precautions, and the development of commercial serologic screening tests have reduced the number of new cases to about 25,000 annually.

An estimated 3.9 million (1.8 percent) Americans have been infected with HCV. Most (75 to 85 percent) are chronically infected. Chronic liver disease usually is insidious, progressing at a slow rate without symptoms or physical signs for 20 or more years. Cirrhosis eventually develops in 10 to 20 percent of chronically infected persons, and hepatocellular carcinoma develops in 1 to 5 percent.

Blood and blood products have been implicated in accidental human infection. The deeper the wound, the greater the chances of infection. Less efficient transfer develops after mucosal exposure. HCV transmission does not seem to occur through intact skin.

HCV infection has followed exposure to solid needles (e.g., suture needles), but the inoculating volume is assumed to be low. The risk is far greater following exposure to hollow bore needles. Blood with elevated HCV RNA levels is more likely to cause disease transmission.

The absolute risks associated with the three major factors (tissue affected, needle type involved, and viral concentration in the source patient) are not well-described. Risk of HCV infection when other factors are present is considered to be very low. Also, survival patterns of HCV on inert environmental surfaces are not known.

Prospective studies suggest that the average risk of HCV transmission after a single needlestick accident is approximately 3 percent (three in 100). In contrast, the likelihood of HIV transmission after a percutaneous exposure is 0.3 percent (one in 333). Unfortunately, there is no available vaccine and no approved methods of preventing HCV infection after an occupational exposure. Thus, HCV infection remains an important occupational hazard for dental personnel.

The prevalence of HCV infection among dentists and oral surgeons averages 1 to 2 percent. This is approximately the same as it is for the general American population. The level of risk for health-care workers (HCWs) regularly exposed to human blood is not known.

The optimal strategy for diagnosing HCV infection after an occupational exposure has not been well-defined. After an exposure, the HCW should be tested at a minimum for the presence of HCV antibodies and serum levels of alanine aminotransferase (ALT). This should be accomplished within a few days of the exposure and will help determine if the HCW is already infected. HCV antibodies are measurable on average 50 to 70 days after exposure. Although variable, HCV RNA is detectable in serum 10 days after exposure. ALT levels also rise quickly after an exposure.

Consider retesting at four to six weeks. Positive laboratory results could cause the early start of treatment or other changes in case management. Testing, especially for antibodies, should be done again four to six months after an exposure to HCV-positive blood. This is considered the optimal means of detecting infection. However, infection is known to have occurred in the absence of seroconversion.

Therapy for hepatitis C is a rapidly changing area of clinical practice. Data suggest that interferon therapy may prevent chronic HCV infection. The most effective treatment is not currently known.

The Organization for Safety and Asepsis Procedures (OSAP) is the leading source for infection control and safety information in dentistry. OSAP recently electronically published valuable information on HCV — Issue Focus: Hepatitis C Virus and Dentistry (www.osap.org/issues/pages/ hepc/index.htm).