Salmonella Typhi IgM (Typhi Dot) Test

Typhoid fever caused by Salmonella typhi is widely recognized as a major public health problem in developing countries. Typhidot is a blood test consisting of an ELISA kit which detects IgM and IgG antibodies against the bacteria Salmonella typhi. The test can show a positive response within 2–3 days of infection. It separately identifies IgM and IgG antibodies. The test determines the presence of specific IgM and IgG antibodies with respect to a 50Kd OMP antigen; that is impregnated on nitrocellulose strips. The presence of IgM indicates recent infection whereas IgG antibodies signify remote infection.

The test is mostly done for patients who reported having a fever for at least 4 days or over a week. This includes taking samples of blood from you. Patients are informed to temporarily stop taking medicines that may affect the test. These medications may include water pills, antacids, and laxatives. Note down any more symptoms you're experiencing and for how long. It would be better if you mention any of your recent international trips. This helps the doctor to understand better what kind of test to be conducted. Also, mention the time period since when you have been suffering from fever.

Typhidot IgG/IgM test is an indirect solid phase immunochromatographic assay for qualitative detection and differentiation of specific IgM and IgG antibodies against Salmonella typhi antigen in human blood, serum or plasma. The result only gives a positive or negative reaction to specific antibodies. The preliminary data on the effectiveness of this test have shown sensitivity and specificity of 95% and 86% respectively. It has a relatively good diagnostic value in children with typhoid fever. Early rising antibodies are predominantly IgM in nature. If specific IgM antibodies are detected instead of IgG or both IgG and IgM in a sample, it serves as a marker for recent infection.

A medical doctor would ask you regarding any clinical symptoms you are experiencing and your prior antimicrobial treatment. A blood test is then conducted with Venipuncture, wherein small amount of blood is taken from your veins. Among adults, up to 25 ml of blood is collected. For children, ≤5 years old 3 to 5 ml of blood is collected. A blood film is also prepared for malaria microscopy test. The blood smear is transported to the laboratory within 2 hrs of collection. When samples are received at the laboratory, serum separator tubes are centrifuged at 3,000 × g for 10 min which is later stored at −20°C for serological testing.