Diagnosis of snake venoms by a reverse latex agglutination test

A reverse latex agglutination test using protein A column purified rabbit antivenom IgG-sensitized latex particles was developed for the detection of the six medically important snake venoms of Thailand. The detection limit of the reverse latex agglutination test was 0.16 to 1.2 micrograms/mL of crude venoms. Cross-reactions with heterologous venoms were observed at concentrations 460 to 16000 times that of homologous venoms. Detection of various snake venoms in clinical specimens was carried out by the reverse latex agglutination test. The sensitivity was 52.5% of the 59 serum samples. There was one (1.69%) false positive sample. The positive detection of venom in wound swabs (26 cases) was 38.5% and was not statistically different from that observed in paired serum samples. Interference from human plasma, serum and urine on the reverse latex agglutination test could be eliminated by adsorption with normal rabbit IgG-coated latex suspension or by heat inactivation at 56 degrees C for 30 min. Prozone effect observed in some sera was eliminated by heat inactivation at 56 degrees C for 30 min. The sensitized latex particles were stable at 4 degrees C and -20 degrees C for at least 3 months. Cycles of freezing-thawing and lyophilization did not change their reactivities. The total test time was about 40 min.