Role of modified Widal test in the diagnosis of enteric fever.

ABSTRACT

OBJECTIVES: To evaluate the diagnostic specificity of modified Widal for recent infection in comparison with conventional Widal test. METHOD: Modified widal test was simultaneously done along with conventional Widal test in serum samples obtained from 50 bacteriologically positive cases of Salmonella typhi infection as well as 50 healthy individuals. RESULTS: A four-fold difference in the titres was noticed in the 50 sera of the test group and no charge in the titres of the control group. The early rising O antibodies which are predominantly IgM in nature. These are due to recent infection and are inactivated by 2-mercaptoethanol. On the other hand H is a mixture of IgG and IgM hence IgM portion gets inactivated giving rise to fall in titre. By inactivating IgM antibodies in modified Widal test, the agglutination would be brought about only by specific IgG while in the conventional Widal test agglutination is due to specific IgG and IgM. The difference in the titres indicates specific IgM class of antibodies which is the hallmark of recent infection. CONCLUSION: If conventional Widal test and modified Widal test are simultaneously done, one can be definite about the diagnosis of enteric fever.