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Are there any specific tests to diagnose typhoid?

Q: Are there any other specific tests for diagnosing typhoid fever other than bacterial culture, as Widal test is non-specific?

A:Diagnosis of enteric fever is usually confirmed by identifying the causative organisms (Salmonella typhi / Salmonella paratyphi or as they are now known - Salmonella enteria serotype Typhi or Paratyphi) in a culture of blood, bone marrow, body fluids or tissue. Blood culture is the mainstay of the diagnosis of this disease. More than 80% of patients with typhoid fever have the causative organism in their blood. For the culture, a small sample of blood, stool, urine or bone marrow is placed in a special culture medium that encourages the growth of bacteria and may be provide the positive report in 36-72 hours. A bone marrow culture often is the most sensitive test for enteric fever and is particularly valuable for patients who have been previously treated, who have a long history of illness and for whom there has been a negative blood culture with the recommended volume of blood. Duodenal aspirate culture is also very good as a diagnostic test but has not found widespread acceptance because of poor tolerance of duodenal aspiration, particularly in children. Stools can be collected from acute patients and they are especially useful for the diagnosis of typhoid carriers. Recent advances in diagnosis of enteric fever include the rapid IDL Tubex test (from a Swedish company), which detects IgM O9 antibodies from patients. Typhidot is another rapid serological test, which takes three hours to perform. It was developed in Malaysia for the detection of specific IgM and IgG antibodies against an antigen of S. typhi. A newer version of the test, Typhidot-M, was recently developed to detect specific IgM antibodies only. The dipstick test (developed in the Netherlands), is based on the binding of S. typhi-specific IgM antibodies in samples to S. typhi lipopolysaccharide (LPS) antigen and the staining of bound antibodies by an anti-human IgM antibody conjugated to colloidal dye particles. These newer tests are under evaluation and may not be available routinely.


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