Clostridium difficile - FAQ
Why the kit doesn't contain loop and tube in the standard packaging?
The standard kit doesn't contain the loop and the plastic tube because that material is very common used in labs. In general labs obtain more competitive prices on the plastic disposable than Coris. Coris can supply the kit containing loot and tube upon specific request; however, it's important to take in account of additional cost related to the plastic material, administration and shipment.
The customer can also use the dropper bottle instead of micropipette without any problems. In the case, an inoculating loop and a 3 or 5mL test tube would be sufficient.
Is the buffer the same for all Coris BioConcept K-SeT kits? If I need some more for my tests, may I use the one from another kit?
According to the "Instructions For Use", it is not allowed to exchange buffer between kits. If you have volume problems, please contact your distributor who is able to provide additional vials. Nevertheless, the buffer is the same within one product of different lot numbers (e.g. Rota-Strip buffers exchange between different lots will not give rise to any problems on the strips).
At present, 8 different kinds of buffers are used in Coris’products, i.e., RE-A Buffer (for Influ –A&B Respi K-SeT), Extraction Buffer (for RSV-Strip), HC Dilution buffer (for Adeno Respi-Strip, Combi-Strip, Pylori-Strip, GastroVir-Strip, for Crypto-Giardia Duo-Strip, Giardia-Strip, and all cassette formats of the corresponding kits), HydroK buffer (for dry swab Test restricted to AdenoRespi K-SeT), ST-A buffer (for C.diff-Strip and Clostridium K-SeT), LY-A Buffer (for RSV Respi K-SeT and for kits RESIST), BL-A Buffer (for HAT Sero K-SeT), ST-1/ST-2 Buffers (for Strep-A Respi-Strip), and Sample Dilution Buffer for all the other products.
Regarding the GastroVir Kit we received some particular comments claiming that the Control Line was too faint. The buffer has been improved to allow a better migration of the latex microspheres leading to a better and a more homogeneous signal. This improvement does not affect any characteristics of the kit (i.e. specificity and sensitivity).
What happens when clinical specimen is a strongly positive specimen? What about the control line?
There are two different kinds of conjugates – a specific reagent for test line and a specific reagent for the control line - in the strip. A strong positive specimen has NO effect on the intensity of the control line onto the nitrocellulose of the strip. As long as the control line appears - with whatever intensity level - the test should be regarded as validated.
Why does the control line sometimes appear very weak while the test line is positive?
Control line is aimed to ensure that chromatography has been performed up to the top of the strip. It is not related with the result of the diagnostic itself.
Sometimes, the control line might be "slightly weak "without any precise reason. It could be only an effect of the sample migration and / or responsiveness at the control line. To sum up, the control line is aimed to validate the test using various specimen exists.
How to use correctly K-SeT kits of Coris BioConcept?
Always store the reagents at the indicated storage temperature : between 4 and 30°C for all kits
Always use gloves to manipulate kit components and samples
Always use the provided (Extraction, Dilution, …) Buffer even if the sample is already diluted (e.g. in a transport medium)
Always be sure that the solution sample – buffer is homogenous before testing
Always read the results when the dipstick into the device is wet (between 10 and 15 minutes depending on the test)
How long a pouch can remain open before performing the test?
Once the pouch is opened, the test should be performed immediately. An unopened pouch may be kept at between 4 and 30°C and used until the shelf-life date indicated on the packaging.
How shall we use positive control with our kits?
Positive control should be used diluted with the provided buffer of the respective kit as recommended in the notice of kit. In practice, dispense 100 µL of prepared control (see instructions for use of such positive controls) into the sample well of the device.
How many tests can be performed with a positive control?
It is various between positive controls forms, e.g. freeze-dried or liquid.
The dilution level of positive control determines the number of possible tests. Please reference it to the Instruction For Use of each positive control.
The liquid does not migrate in the cassette, what should I do?
If the sample does not migrate, it may be due to an excessive amount of specimen taken by the Faecal Sampling System and / or caused by the presence of excessive particulate matter of diluted specimen. To solve the issue, fill any tube with the diluted specimen and then performs a centrifugation step before collecting supernatant and run on a new testing device.
Is it a problem if the test has "run" more than the recommended time?
Yes. It might cause the appearance of false positive signal on test line due to a reverse-flow of liquid from upper part to lower part of dipstick embedded into the cassette.
The signal of the test line is very weak in comparison with the control line. Do I have to consider that the result is positive?
The control line is aimed to ensure the user that the chromatography is performed up to the top of the strip. It does not give any indication on the diagnostic result. Whenever a signal is observed on the test line (weak or strong), it means that the sample is positive for the pathogen of interest.
What is the EQA procedure to be used with our rapid kits?
Using a lab pipette, transfer exactly 480 μL of the dilution buffer solution into a tube.
Add 20 μL of liquid EQA sample or 1 loop of 10µl of solid EQA sample.
Vortex the preparation to homogenize. The entire sample must be suspended into the solution.
Strip format: dip the sensitized strip in the direction indicated by the red arrow
Cassette format: dispense 100 μL of diluted sample into the sample well of the device using a lab pipette.
Leave to react accordingly to the instructions for use of the kit.