Typhidot

Typhidot is a medical test consisting of a dot ELISA kit that detects IgM and IgG antibodies against the outer membrane protein (OMP) of the Salmonella typhi. The typhidot test becomes positive within 2-3 days of infection and separately identifies IgM and IgG antibodies.

Procedure

The patient's serum is added to a test device containing Salmonella typhi OMP antigen. If specific IgM or IgG antibodies are present in the patient's serum, they bind to the antigen. The bound antibodies are then detected by using anti-human IgM or anti-human IgG antibodies, which are linked to colloidal gold. The appearance of a pink color dot indicates a positive result while its absence indicates a negative result.

Interpretation

• IgM positive: Indicates current infection.
• IgG positive: Indicates past infection or immunization.
• Both IgM and IgG positive: Indicates either current infection with past exposure/immunization or false positive results.

Advantages

• The test is easy to perform, and results can be obtained within 2-3 hours.
• It can be performed in the early stage of infection before the Widal test becomes positive.
• It is more reliable and specific than the Widal test.

Disadvantages

• It is not quantitative; it is either positive or negative.
• It may remain positive for a long time after the patient has recovered from typhoid, thus it cannot be used to judge the effectiveness of treatment or for follow-up.

See Also

• Widal test
• Salmonella typhi
• Typhoid fever