Is the skin sensitivity test required for administering equine rabies immunoglobulin?

BACKGROUND: Rabies immunoglobulins are life-saving in patients with severe exposure to rabies. Despite the high degree of purification of equine rabies immunoglobulin (ERIG), the product inserts still recommend a skin sensitivity test before administration of this heterologous serum. A recent WHO recommendation states that there are no scientific grounds for performing a skin test before administering ERIG because testing does not predict reactions and it should be given irrespective of the result of the test. In this conflicting situation, we assessed the use of the skin sensitivity test in predicting adverse events to ERIG. METHODS: The data analysed were from the Antirabies Clinic of the Kempegowda Institute of Medical Sciences Hospital, Bengaluru, India. The period of study was 26 months (June 2008-July 2010). The skin sensitivity test was validated by evaluating its sensitivity, specificity, predictability, falsepositive and false-negative results. RESULTS: A total of 51 (2.6%) adverse events were reported in 31 (1.5%) subjects. Most of these were mild to moderate in nature and subsided without medication. There was no serious adverse event. The sensitivity and specificity of the skin sensitivity test to predict an adverse event was 41.9% and 73.9%, respectively. CONCLUSION: Our experience with the skin sensitivity test suggests that it may not be required before administering ERIGs, as recommended by WHO.