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Salmonella Antigen Test Clinical Study

Time:13 September 2016 Click:611

1. Profile
Salmonella belongs to enterobacteriaceae, it is a conditional intracellular parasitism gram-negative enteric bacilli, it is (0.6~0.9) × (1~3) um in size, without spore and usually without capsul, most of them have flagellum except Salmonella pullorum and salmonella gallinarum. Salmonella is a pathogen for both human and animal. It can cause not only white diarrhea of chicks, necrotic enteritis, abortion etc for animal, but also typhoid, paratyphoid, ichoremia, gastroenteritis, and food-poisoning for human. It is an important pathogen of bacteria food poisoning.

Salmonella is regarded as one of the more important food borne pathogens worldwide, seriously threatening human and animal health. It has become a common problem of public health. In both human and animal,   separation rate of Salmonella enteritidis is relatively high, which mainly cause food gastroenteritis for animal or gastroenteritis and food poisoning for human. It is mainly spread by food for human infection of Salmonella. Meat, eggs, egg products, unpasteurized milk, milk product, sea food etc are all related to Salmonella disease. Human Salmonella disease symptoms are sicchasia, vomit, diarrhea, abdominal pain or cramp, fever and headache. Incubation is from 8 to 72 hours. It usually occurs in 12 to 36 hours after taking infected food, and the symptom can remain for 1 week.

Therefore, it is important to diagnose Salmonella in time, which can provide necessary and accurate treatment.

The Salmonella Antigen Test developed by Shanghai Chemtron Biotech Co.,Ltd is a chromatographic immunoassay and adopts double antibody sandwich method to qualitatively detect Salmonella antigen in human stool specimen. It can be used as an aid to diagnose Salmonella infection.

The Salmonella Antigen Test  developed by Shanghai Chemtron Biotech Co.,Ltd adopts immuno chromatographic technology and double antibody sandwich method for the qualitative detection of Salmonella antigen in human stool specimens.
The nitrocellulose membrane is pre-coated with anti-Salmonella monoclonal antibody-2 on the test region and goat anti-mouse IgG polyclonal antibody on the control region. The glass fiber paper is pre-coated with anti-Salmonella antibody-1–latex conjugate.

During test, for Positive result, Salmonella antigen in specimen will combine with anti Salmonella monoclonal antibody-1 latex conjugate first, and this mixture moves forward by capillary action and will be captured by anti Salmonella monoclonal antibody-2 immobilized on test region, and forms a red colored line on it. Absence of red colored line in the test region indicates Negative result, i.e Salmonella antigen is not present in the specimen or lower than the detection limit of the test.

A second red control line will always appear in the result window to indicate that the test has been correctly performed and the test device functions properly. If the control line does not appear, the test is invalid. The presence of this red-colored line serves as:  1) Verification that sufficient volume is added.  2) Proper flow is obtained.

As investigated in China FDA database, no domestic or foreign manufacturers have registered same product. 4 domestic manufacturers have registered products related to Salmonella detection, but all of them are PCR fluorescence method.

2、Purpose of the Study
By comparing with Clinical Gold Standard (Culture), evaluate the sensitivity, specificity, consistency of the Salmonella Antigen Test of Shanghai Chemtron Biotech Co.,Ltd.

3、Management of the Study
The study is conducted, organized and administrated by three hospitals according to Medical Device Clinical Test Management, Guidance of Clinical Study of In Vitro Diagnostic reagent, Clinical Laboratory Quality Control Principle, etc, to select related researchers, establish related quality control method, and ensure the scientificalness and strictness of the study.

4. Design of the Study
The Salmonella Antigen test belongs Class III IVD products, the clinical study is conducted according to related regulations of China FDA to IVD products, including, Management of IVD registration and Guidance of Clinical Study of IVD products.   4.1 Specimens of the Study
Totally 1038 pcs specimens are analyzed in this study.
4.2 Specimen collection
4.2.1 Collect specimen in dry, clean and waterproof containers.
4.2.2 Unscrew the sample collection tube, use the applicator stick attached on the cap to transfer small piece of stool into the specimen collection tube. Collect enough stool specimen from different angel.
4.2.3  Replace the stick into the tube and tighten securely. Mix the specimen with collection buffer.
4.2.4 Specimen should be tested immediately after collection, if unable to test immediately, store at 2℃-8℃ for 72 hours or -20℃ for longer period.
4.2.5 Recover to room temperature before testing. Refrigerated specimen must be thawed completely, and recover to room temperature and mixed thoroughly. Repeated freezing and thawing of specimens is not recommended and may cause erroneous results.

4.3 Test material and Comparison Method
4.3.1 Product for study
Salmonella antigen test, LOT: B201402213, EXP: 2016.02.25, manufactured by Shanghai Chemtron Biotech Co.,Ltd
4.3.2 Comparison Method
Compare with Culture, provided by each hospital.

4.4 Method for the study
Synchronous blind test is adopted for the study. Each specimen is test by Chemtron Salmonella antigen test and Culture, record the test results.
Chemtron Salmonella antigen test is performed according to instruction manual, and Culture is performed according to hospital guidance.

4.5 Analysis of Test Results
Record all original test results, including patient name, id, age, gender, specimen, test result, etc.
Analyze the data after testing by each hospital. Evaluate and confirm the reliability of the product in clinical use.
The evaluation standard of the study is sensitivity, specificity and consistency.
Sensitivity(Real positive rate)=A/(A+C)×100%
Specificity(Real negative rate)=D/(B+D)×100%
Consistency=(A+D)/(A+B+C+D)×100%

Analyze Kappa by using above Square Table. Kappa>0.8 means highly consistent, it is regarded 2 systems are in equivalent effectiveness. 0.40.8

5. Test Results
5.1  Test result
Take Culture as reference: Among 1038 specimens, Chemtron Salmonella antigen test positive results 325 pcs, negative results 713 pcs. Culture positive results 332 pcs, negative results 706 pcs.
Take Culture as reference, Chemtron Salmonella Antigen Test:
Sensitivity = 325/(325+7)×100% = 98.49%
Specificity = 706/(0+706)×100% = 100%
Consistency=(325+706)/(325+0+7+706)×100% = 99.33%
Input the below table into SPSS15 system to calculate KAPPA and analyze the equivalence of 2 methods. KAPPA result: KAPPA=0.968. Chemtron Salmonella Antigen test has high consistency with Culture.

5.2 Unconsistent result analysis
7 test results are not in consistent with Culture, Culture is positive while Chemtron Salmonella antigen test is negative. It is confirmed that the Culture result is correct. Because of the limitation of rapid test, it is unable to be completely accurate, it requires other methods as an aid in diagnose or confirmation. However, the product is acceptable for clinical use as an aid to diagnose salmonella infection.

6. Conclusion
The study indicates that the Salmonella test developed by Shanghai Chemtron Biotech Co.,Ltd has good consistency with Culture, sensitivity is 98.49%, Specificity 100%, Consistency 99.33% . It can be used as an aid for clinical diagnose of Salmonella infection.