The Widal Test, also known as the tube agglutination test, is a diagnostic laboratory procedure used to detect the presence of antibodies against certain bacteria that cause typhoid fever and other related illnesses. The test is based on the principle of agglutination, which involves the clumping together of specific bacteria in the presence of corresponding antibodies. The procedure involves mixing a patient’s serum sample with a suspension of the bacteria and observing the formation of clumps or agglutination. The results are interpreted based on the titer or concentration of antibodies detected in the serum sample. The Widal Test is a valuable tool in the diagnosis of typhoid fever and can also help in monitoring the effectiveness of treatment. However, it is important to note that the test can produce false-positive or false-negative results, and should be interpreted in conjunction with other clinical and laboratory findings.