The Widal test measures the levels of specific antibodies against Salmonella typhi and Salmonella paratyphiantigens in a blood sample.It helps identify an infection when the patient presents symptoms like prolonged fever, abdominal pain, and weakness.

This test is mainly used in regions with a high prevalence of typhoid fever.There's a risk of false positives in areas where Salmonella exposure is common or if the patient has received prior vaccination against typhoid.The Widal test is generally not recommended as a stand-alone diagnostic test due to potential cross-reactivity with other bacteria and previous infections.

Normal Range:

• Typically, titers less than 1:80 are considered normal, though this can vary by region and laboratory.
• Titers of 1:160 or higher are often indicative of an active infection, though serial testing (two samples taken over 7–10 days) showing a significant rise in titers is more reliable.

Interpretation:

• O antibody titer: Indicates acute infection; levels rise during the initial stages of infection.
• H antibody titer: Indicates past or current infection and may persist longer.
• A fourfold increase in titers between two tests over a 7–10 day period can confirm an active infection.
• High titers without a rising trend may indicate past exposure or vaccination rather than current infection.

Blood Serum: Collected from a blood sample for analysis in the laboratory.