Typhoid IgG/IgM Rapid Test-Cassette (Serum / Plasma)
This test follows the lateral flow immunoassay for the simultaneous detection and differentiation of the anti-Salmonella Typhi (S. Typhi) IgG and IgM present in the human serum or plasma. It is used as a screening test and as an aid in the diagnosis of infection with S. Typhi. Any reactive specimen with the Typhoid IgG or IgM 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, 17 million cases have been estimated worldwide and 600,000 associated deaths occur annually. Patients who are infected with HIV are at increased risk of clinical infection with S. Typhi. Evidence of H. Pylori infection also increases the risk of acquiring typhoid fever. 1 to 5% patients become chronic carrier harboring S. Typhi in the gallbladder.
The clinical diagnosis of the typhoid fever depends upon the isolation of S. Typhi from the blood, bone marrow or a specific anatomic lesion. In the facilities that cannot afford to perform this complicated and time consuming procedure, Filix-Widal test is used to facilitate the diagnosis. However, due to many limitations lead to difficulties in the interpretation of the Widal test.
In contrast, this Typhoid IgG/IgM Rapid Test kit is a simple and rapid laboratory test. The test can simultaneously detect and differentiate the IgG and the IgM antibodies to S. Typhi specific antigens and used to aid in the detection of current or previous exposure to the S. Typhi.
This test follows a lateral flow chromatographic immunoassay. The test cassette consists of:
A burgundy colored conjugate pad contain recombinant S. Typhoid H and O antigen conjugated with colloidal gold (Typhoid conjugates) and rabbit IgG-gold conjugates.
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 precoated with the reagent for the detection of IgG anti S. Typhi and C band is precoated with goat-anti-rabbit IgG.
When an adequate volume of the test specimen is dispensed into the sample well of the cassette, the test specimen migrates by the capillary action across the test cassette. Anti S. Typhi IgM if present in the sample bind to the Typhoid conjugates. The immunocomplex is then captured on the membrane by the pre-coated anti-human IgM antibody, form a burgundy colored M band, indicating an S. Typhi IgM positive test result.
Absence of any test band indicates a negative result. The test contains an internal control, which should develop a line regardless of any color development on any of test bands. Otherwise, the test result will be invalid and the sample must be retested with another device.
REAGENTS AND MATERIALS PROVIDED
Each kit contains 25 or 30 test devices, each sealed in a pouch with three items inside:
One cassette device
One plastic dropper
Sample Diluents (1 bottle, 5mL)
One package inserts (instruction for use)
MATERIALS MAY BE REQUIRED AND NOT PROVIDED
Positive Control (1 vial, red cap, 1mL)
Negative Control (1 vial, green cap, 1mL)
MATERIALS REQUIRED BUT NOT PROVIDED
Clock or Timer
WARNINGS AND PRECAUTIONS
It is used for in-vitro diagnostic only.
The package insert must be read completely before performing the test. Failure to follow gives inaccurate test results.
Do not open the pouch, unless ready to conduct the test.
Do not use expired devices.
Bring all the reagents to room temperature (15°C to 30°C) before use.
Do not use the components of the kit in any other type of the test as a substitute.
Do not use hemolyzed blood specimen for testing.
Wear protective clothing and disposable gloves while handling the reagents and specimens. You’re your hands thoroughly after performing the test.
Users should follow the US CDC Universal Precautions for prevention of transmission of HIV, HBV and other blood-borne pathogens.
Avoid smoking, drinking, or eating in the areas where the specimens or kit reagents are being handled.
Dispose of all the specimens and materials that are used to perform the test as bio-hazardous waste.
Handle the Negative and Positive Control in the same manner as it has patient’s specimens.
The testing results should be read within 15 minutes after the specimen is applied to the sample well or sample pad of the device. Reading the result after 15 minutes may give erroneous results.
Do not perform the test in a room with strong air flow, like with an electric fan or strong air-conditioning.
REAGENT PREPARATION AND STORAGE INSTRUCTIONS
All reagents are ready to use, store the unused test devices unopened at 2°C to 30°C. The positive and negative controls should be kept at 2°C to 8°C. If stored at 2°C to 8°C, ensure that the test device is brought to room temperature before testing. The test device is stable through the expiry date printed on the sealed pouch. Do not freeze the kit or expose over 30°C.
SPECIMEN COLLECTION AND HANDLING
Consider any specimen of human origin as infectious and handle them using standard bio-safety procedures.
Collect the blood specimen into lavender, blue or green top collection tube (containing EDTA, citrate or heparin, respectively in Vacutainer) by venipuncture.
Separate the plasma by centrifugation.
Withdraw the plasma into a new pre-labeled tube.
Collect the blood specimen into a red top collection tube (containing no anticoagulants in Vacutainer) by venipuncture.
Allow the blood to clot.
Separate the serum by centrifugation.
Withdraw the serum into a new pre-labeled tube.
Test the specimens as soon as possible after collecting, if not then store at 2°C to 8°C up to 5 days. For more than 5 days the specimens should be frozen at -20°C, avoid multiple freeze-thaw cycles. Prior to testing, bring the frozen specimens to room temperature slowly and mix gently. Specimens containing particulate matter should be clarified by centrifuge prior to testing. Do not use samples demonstrating gross lipemia, turbidity or gross hemolysis in order to avoid interference on the result interpretation.
Step 1: Make sure the specimen and the test components are at room temperature.
Step 2: When ready for testing, open the pouch at the notch and remove the device. Place the test device on a clean, dry and flat surface.
Step 3: Be sure to label the device with the ID number.
Step 4: Fill the pipette dropper with the sample.
Hold the dropper vertically and dispense 1 drop (about 30 to 45μL) of the specimen into the sample well make sure that there are no air bubbles.
Now add 1 drop (about 35 to 50μL) of the sample diluents immediately.
Step 5: Set up the timer.
Step 6: After 15 minutes read the results. Positive results are visible within 1 minute.
Don’t read the results after 15 minutes and to avoid any confusion, discard the test device after interpreting the result.
1-Internal Control: This test contains a built-in control feature, the C line; it develops after adding the specimen and sample diluents. Otherwise, review the whole procedure and repeat the test with a new device.
2-External Control: Good laboratory practice recommends using the external controls, positive and negative; to assure that the proper performing of the assay has been done, particularly, under the following circumstances:
New operator uses the kit, before performing testing of specimens.
A new lot of test kit is used before.
A new shipment of kits is used.
The temperature used during storage of the kit fall outside of 2 to 30°C
The temperature of the test area falls outside of 15 to 30°C
INTERPRETATION OF ASSAY RESULT
Negative or Non-Reactive Result: If only the C band appears, the absence of any burgundy color in both the test regions (M and G) indicates that no anti-S. Typhi antibody is detected in the specimen. The result is negative or non-reactive.
Positive or Reactive Result:
In addition to the presence of C-line, if only M line is developed, the test indicates for the presence of anti- S. Typhi-IgM present in the specimen. The result is positive or reactive.
In addition to the presence of C-line, if only G line is developed, the test indicates for the presence of anti- S. Typhi-IgG present in the specimen. The result is positive or reactive.
In addition to the presence of C-line, both M and G lines are developed, the test indicates for the presence of anti-S. Typhi-IgG and IgM present in the specimen. The result is positive or reactive.
Samples with positive or reactive results should be confirmed with an alternative testing method(s) and clinical findings before a positive determination is made.
Invalid: If no C-line, the assay is invalid regardless of any burgundy color in the test line as indicated below. Repeat the assay with a new device.
Clinical Performance for IgM Test
Total of 334 samples from susceptible subjects was tested by this Rapid Test kit and by a commercial S. Typhi-IgM EIA kit. Comparison of all subjects is showed in the following table.
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Typhoid IgG/IgM2.0 Rapid Test
Relative Sensitivity: 91%, Relative Specificity: 99.3%, Overall Agreement: 98.5%
Clinical Performance for IgG Test
Total of 314 samples from susceptible subjects were tested by this Rapid Test kit and by a commercial S. Typhi-IgG EIA kit. Comparison of all subjects is showed in the following table.
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Typhoid IgG/IgM2.0 Rapid Test
Relative Sensitivity: 92.9%, Relative Specificity: 99.3%, Overall Agreement: 99.0%
LIMITATIONS OF TEST
The assay procedure and the test result interpretation must be followed very closely while testing the presence of antibodies to S. Typhi in the serum or plasma from individual subjects. Failure in following the procedure might give inaccurate results.
Typhoid IgG/IgM2.0 Rapid Test is limited to the qualitative detection of the antibodies to S. Typhi present in the human serum or plasma. The intensity of the test band does not have linear correlation with the antibody titer present in the specimen.
The Typhoid IgG/IgM2.0 Rapid Test also detects paratyphoid antibodies.
A negative result indicates absence of detectable anti-S. Typhi antibodies present in the sample. However, negative test results do not preclude the possibility of exposure to S. Typhi.
A negative result can occur if the quantity of anti-S. Typhi antibodies present in the sample are below the detection level, or the antibodies that are detected are not present during the stage of disease in which a sample is collected.
If the symptom persists, while the result is negative or nonreactive, it is recommended to re-sample the patient few days later and test with an alternative test method, such as bacterial culture method.
Some specimens contain unusually high titer of heterophile antibodies or rheumatoid factor may affect expected results.
The results obtained with this test should only also be interpreted with other diagnostic procedures and clinical findings.