Antibodies against Equine influenza (EI) are traditionally quantified by haemagglutination inhibition (HI) or single
radial haemolysis (SRH) .Both assays measure antibodies against haemagglutinin. HI test has the advantage of good
sensitivity and the results can be obtained within hours. SRH method is of considerable potential value for the
serologic diagnosis and surveillance of influenza, as the test performed with undiluted and untreated serum. In order
to determine the sensitivity, accuracy and specificity of SRH, 50 serum samples from horses and 15 from G. pigs
vaccinated with inactivated equine influenza vaccine were assayed for antibodies by both HI and SRH tests. The
proportion of horse serum samples that gave positive SRH reactions and HI were 74 % and samples gave negative
result by both tests was 14%.The proportion of symmetry (88%). Serum samples of guinea-pigs with high HI titer
gave potent SRH reaction. So it is clear that antibody concentrations specific for equine influenza virus measured
using SRH are highly correlated with HI assays and combines the sensitivity of HI test with higher accuracy.