Influence of modifications in widal test methodology on antibody titres

– Widal test is still one of the leading test for diagnosis of enteric fever in developing countries. The study compared semi-quantitative slide Widal with conventional tube Widal and evaluated role of modified Widal using 2 Mercaptoethanol (2ME). 80 serum samples were tested using both methods. Modified Widal was performed on the serum samples with suggestive titre for typhoid fever. Slide Widal and tube Widal methods showed good agreement (kappa value 0.89) in detecting suggestive titre for typhoid fever. The sensitivity of slide method was 91%, and specificity was 100% as compared to tube method. Suggestive titres for Typhoid fever were observed in 42 (52.5%) samples by slide method and in 46 (57.5%) samples by tube method. The sensitivity of both methods was 87.5% considering blood culture as gold standard. The specificity of slide method was 56.3%, and tube method was 50%. Four-fold decrease in titre was observed in 28/32 (87.5%) for O antibodies and 30/32 (93.8%) samples for H antibodies, indicating recent infection. Slide Widal can be used as an alternative to tube method for rapid results. However, tube method is ideal for obtaining the accurate titre value. Performing modified Widal parallel to conventional Widal will help in differentiating acute from chronic cases.