Present tests for detection of snake venom: clinical applications

Immunologic tests for detection of snake venom and venom antibodies have important clinical applications. Enzyme-linked immunoassay (ELISA) and radioimmunoassay (RIA) provide adequate specificity and sensitivity. The former is much more widely used because it is inexpensive, relatively easy to perform, and uses stable reagents. Some ELISA systems will detect 0.5 ng of venom; however, a sensitivity of 10 to 100 ng is more usual. Minimum running time is 30 to 45 minutes; with longer times, greater sensitivity can be attained. Wound aspirate, serum, and urine are the most suitable materials for venom detection. ELISA has been used for clinical diagnosis of snakebite, to monitor antivenom dose, to study clinical syndromes associated with envenomation, to detect venom in forensic cases, and to evaluate first aid techniques. The indirect ELISA usually is used for detecting and titrating venom antibody. This is potentially useful in epidemiological studies of snakebite incidence, in evaluating potency and paraspecific activity of antivenoms, and in studying response to venom immunogens. Current ELISA systems involving snake venoms have low specificity, and most cannot reliably differentiate venoms of related snakes. Venom antibody detection assays are less satisfactory than those for venom; nonspecific reactions and cross-reactivity are unacceptably high. Methods for improvement of snake venom immunodiagnosis are discussed.