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Typhoid IgG/IgM Rapid Test Cassette (Serum / Plasma)
Cat. No.: RA0603I
The Typhoid IgG/IgM Rapid Test is a lateral flow immunoassay for the simultaneous detection and differentiation of anti-Salmonella typhi (S. typhi)G and IgM in human serum or plasma. It is intended to be used as a screening test and as an aid in the diagnosis of infection with S. typhi. Any reactive specimen with the Typhoid IgG/IgM 2.0 Rapid Test must be confirmed with alternative testing method(s).
Summary and Explanation of the Test
Typhoid fever is caused by S. typhi, a Gram-negative bacterium. World-wide an estimated 17 million cases and 600,000 associated deaths occur annually1. Patients who are infected with HIV are at significantly increased risk of clinical infection with S. typhi2. Evidence of H. pylori infection also presents an increase risk of acquiring typhoid fever. 1-5% of patients become chronic carrier harboring S. typhi in the gallbladder.
The clinical diagnosis of typhoid fever depends on the isolation of S. typhi from blood, bone marrow or a specific anatomic lesion. In the facilities that can not afford to perform this complicated and time-consuming procedure, Filix-Widal test is used to facilitate the diagnosis. However, many limitations lead to difficulties in the interpretation of the Widal test3,4.
In contrast, the Typhoid IgG/IgM Rapid Test is a simple and rapid laboratory test. The test simultaneously detects and differentiates the IgG and the IgM antibodies to S. typhi specific antigen5 thus to aid in the determination of current or previous exposure to the S. typhi.
The Typhoid IgG/IgM Rapid Test is a lateral flow chromatographic immunoassay. The test cassette consists of: 1) a burgundy colored conjugate pad containing recombinant S. typhoid H antigen and O antigen conjugated with colloid gold (Typhoid conjugates) and rabbit IgG-gold conjugates, 2) a nitrocellulose membrane strip containing two test bands (M and G bands) and a control band (C band). The M band is pre-coated with monoclonal anti-human IgM for the detection of IgM anti-S. typhi, G band is pre-coated with reagents for the detection of IgG anti-S. typhi , and the C band is pre-coated with goat anti rabbit IgG.
When an adequate volume of test specimen is dispensed into the sample well of the cassette, the test specimen migrates by capillary action across the test cassette. Anti-S. typhi IgM if present in the patient specimen will bind to the Typhoid conjugates. The immunocomplex is then captured on the membrane by the pre-coated anti-human IgM antibody, forming a burgundy colored M band, indicating a S. typhi IgM positive test result.
Anti-S. typhi IgG if present in the patient specimen will bind to the Typhoid conjugates. The immunocomplex is then captured by the pre-coated reagents on the membrane, forming a burgundy colored G band, indicating a S. typhi IgG positive test result.
Absence of any test bands (M and G) suggests a negative result. The test contains an internal control (C band) which should exhibit a burgundy colored band of the immunocomplex of goat anti rabbit IgG/rabbit IgG-gold conjugate regardless of the color development on any of the test bands. Otherwise, the test result is invalid and the specimen must be retested with another device.
Reagent and Materials Provided
a. One cassette device.
b. One plastic dropper.
c. One desiccant.
2. Sample Diluent (1 bottle, 5 mL)
Materials May Be required and not provide
Materials required but not provided
Warnings and Precautions
For in Vitro Diagnostic Use
Reagent Preparation and storage instructions
All reagents are ready to use as supplied. Store unused test devices unopened at 2°C-30°C. The positive and negative controls should be kept at 2°C-8°C. If stored at 2°C-8°C, ensure that the test device is brought to room temperature before opening. The test device is stable through the expiration date printed on the sealed pouch. Do not freeze the kit or expose the kit over 30°C.
Specimen Collection and Handling
Consider any materials of human origin as infectious and handle them using standard biosafety procedures.
1. Collect blood specimen into a lavender, blue or green top collection tube (containing EDTA, citrate or heparin, respectively in Vacutainer® ) by veinpuncture.
2. Separate the plasma by centrifugation.
3. Carefully withdraw the plasma into new pre-labeled tube.
Test specimens as soon as possible after collecting. Store specimens at 2°C-8°C if not tested immediately.
Store specimens at 2°C-8°C up to 5 days. The specimens should be frozen at -20°C for longer storage.
Avoid multiple freeze-thaw cycles. Prior to testing, bring frozen specimens to room temperature slowly and mix gently. Specimens containing visible particulate matter should be clarified by centrifugation before testing. Do not use samples demonstrating gross lipemia, gross hemolysis or turbidity in order to avoid interference on result interpretation.
Step 1: Bring the specimen and test components to room temperature if refrigerated or frozen. Mix the specimen well prior to assay once thawed.
Step 2: When ready to test, open the pouch at the notch and remove device. Place the test device on a clean, flat surface.
Step 3: Be sure to label the device with specimen’s ID number.
Step 4: Fill the pipette dropper with the specimen.
Holding the dropper vertically, dispense 1 drop (about 30-45 mL) of specimen into the sample well making sure that there are no air bubbles.
Then add 1 drop (about 35-50 µL) of Sample Diluent immediately.
1 drop of specimen 1 drop of sample diluent 15 minutes
Step 5: Set up timer.
Step 6: Results can be read in 15 minutes. Positive results can be visible in as short as 1 minute.
Don’t read result after 15 minutes. To avoid confusion, discard the test device after interpreting the result.
This test contains a built-in control feature, the C band. The C line develops after adding specimen and sample diluent. Otherwise, review the whole procedure and repeat test with a new device.
Good Laboratory Practice recommends using the external controls, positive and negative, to assure the proper performing of the assay, in particularly, under the following circumstances:
a. New operator uses the kit, prior to performing testing of specimens.
Interpretation of Assay Result
2. POSITIVE OR REACTIVE RESULT:
In addition to the presence of C band, both M and G bands are developed, the test indicates for the presence of anti-S. typhi IgG and IgM in the specimen. The result is both IgG and IgM positive or reactive.
Samples with positive or reactive results should be confirmed with alternative testing method(s) and clinical findings before a positive determination is made.
1. Clinical Performance For IgM Test
A total of 334 samples from susceptible subjects were tested by the Typhoid IgG/IgM2.0 Rapid Test and by a commercial S. typhi IgM EIA. Comparison for all subjects is showed in the following table.
|Typhoid IgG/IgM2.0 Rapid Test|
Relative Sensitivity: 91% , Relative Specificity: 99.3%, Overall Agreement: 98.5%
2. Clinical Performance For IgG Test
A total of 314 samples from susceptible subjects were tested by the Typhoid IgG/IgM2.0 Rapid Test and by a commercial S. typhi IgG EIA kit. Comparison for all subjects is showed in the following table.
|Typhoid IgG/IgM2.0 Rapid Test|
Relative Sensitivity: 92.9% , Relative Specificity: 99.3%, Overall Agreement: 99.0%
Limitations of Test
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