Value of skin testing for predicting reactions to equine rabies immune globulin.

The research paper discusses the economic feasibility and safety aspects of using equine rabies immune globulin for rabies treatment in developing countries, highlighting specifically the reliability of skin testing for determining potential allergic reactions before the actual treatment.

Problem Overview

• The study was prompted by the high cost of postexposure prophylaxis (PEP) for rabies, a factor that has led to inadequate treatment in developing countries.
• An alternative is the use of equine rabies immune globulin, which is cheaper than human rabies immune globulin.
• A major safety concern is the risk of fatal anaphylaxis, a severe allergic reaction, which can occur with the administration of heterologous serum (serum derived from a different species).

Skin Testing Concerns

• Authoritative sources recommend skin testing before administration of the equine rabies immune globulin to predict potential allergic reactions.
• However, this research suggests that the strategies and interpretations for skin testing vary greatly and reliable guidelines are yet to be established.

Research Process

• The researchers embarked on a long-term study to develop guidelines for skin test administration, its subsequent interpretation, and finally, determine a cost-benefit ratio.
• The skin test’s function is to predict potential allergic reactions; it does not predict the onset of serum sickness, a reaction to the injection of foreign proteins or serum.
• Modern purified and pepsin-digested equine rabies immune globulins induce rare anaphylactic reactions.
• The authors consider a skin test to be positive for potential allergic reaction only if a wheal (swelling) of more than 10 mm in diameter (with or without flare) or a wheal of 5-10 mm in diameter with a flare of more than 20 mm develops.

Future Considerations

• Despite these findings, the authors note that long-term studies are required to answer remaining questions related to testing criteria and cost benefits of equine rabies immune globulin use, and the reliability of skin testing in predicting allergic reactions.