When dipping  the stick in diluted sample, the level of sample passes beyond the limit indicated by the arrows at the back of the stick. Is there any consequences on the test reactivity?

The red arrow indicates the limit that could not be passed beyond during any incubation.
Depending on the assay tube used routinely in laboratories, it could happen that the limit line indicated on the sticker could be overcome. It cannot give rise to any problems on the result itself, provided the limit indicated by the red arrow on the figure is not passed. The gold conjugate is placed at 2cm from the bottom of the stick. Incubation limit should not exceed 1cm, i.e. the green line indicated on the figure.

What happens when faecal specimen is highly positive? What about the control line?

When a strong positive is to be detected, almost all conjugates are bound to viruses and remain on the specific antibody (lower line) coated onto the nitrocellulose, giving rise to a strong dark-red signal. As a consequence, quantity of remaining gold conjugate that should come to react with the control reagent (upper line) is not enough to give rise to a visible signal. Thus control line appears too weak or even sometimes is not visible by eyes. Even if the control line is very weak, the test is regarded as valid.

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.

Control line may sometimes be "very weak" when the sample is highly positive.
Signal on the control line comes from the remaining conjugate that didn't react with the antigen on the specific live.
More positive will be the specific signal, less positive will be the signal on the control line.

The control line confirms that migration proceeded successfully even if the line is only slightly rose or dark red.

Cuando se introduce una varilla en la muestra diluida, el nivel de la dilución sobrepasa el límite indicado por las flechitas que se encuentran en la parte trasera de la varilla. Puede plantear problema?

Cuando se sumerge una varilla dentro del tampón de dilución para llevar a cabo un test, hay que prestar atención en NO sobrepasar la línea horizontal que se encuentra debajo de las flechitas rojas.
En algunos casos, todo depende de la talla del tubo de ensayo utilizado, puede ocurrir que el límite de esta ínea horizontal sea sobrepasado. No plantea ningún problema para la lectura de los resultados mientras el tampón de dilución no llega a la gran flecha roja del dibujo (es decir debajo del conjugado de particulas de oro). Este conjugado se encuentra colocado a 2 centimetros del borde inferior de la varilla. Hay que tener cuidado en no sumergir la varilla más alla de 1 centimetro, como lo indica la gran flecha verde del dibujo.

Why is stability relatively short after opening?

Indeed the product is stable during at least 15 weeks after first opening. 15 weeks is quite high : that means less than 2 tests per week. Stability is dependant of the storage conditions.
Immunochromatographic test uses nitrocellulosic support which is sensitive to humidity.
That's why we put dessicant in the tube and in the cap.
If the storage is done under dry condition, stability is higher than 15 weeks.
In each case, there is an internal control (upper line). If this internal control appears during the run, that means that the test is running well. We have to give a shelf life, but the test can be used after 15 or 20 weeks. The result will be valid if the control line appears.

How shall we use the RSV positive control?

The positive control should be used diluted 2 times with the extraction buffer (1v/1v). The first extraction period is not necessary. You just have to prepare the dilution, to plunge directly the strip into the dilution, and to wait for 15 minutes.

How many tests can be performed with a positive control?

We recommend having 500µl of solution for one test. To perform a test, we mix 0.25mL of positive control with 0.25mL of dilution buffer (to obtain500µl). If you have 1ml of positive control, you can perform 4 tests ; 2mL of positive control, 8 tests.

The liquid does not go up the strip.

If the sample does not migrate (presence of particles), centrifuge the diluted sample. Collect the culture supernatant and perform the test again.

Is the Toxo-Strip test still valid even if the amplification mix arrives defrosted?

No.

Can the Adeno-Strip kit be used in the urine?

No, only in faeces.

Is it a problem if the test has "run" more than the recommended time?

Yes. You may find false positives.

Which is the necessary water volume needed to make a nasopharyngeal wash?

2mL.

Can I work with bloody nasopharyngeal samples?

Yes, some tests have been performed with such kind of samples with expected results. So, it does not seem to be a problem.

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 chromatography has been performed up to the top of the strip. It does not give any indication on the diagnostic itself.

Whenever a signal is observed on the test line (weak or strong), it means that the sample is positive for the pathogen of interest.

In some cases, when sample is highly positive, the majority of gold conjugate stops at the test line. And only the remaining part migrates to the control line, which explains why the control line could be sometimes weak. If the test line is positive, the test is positive even if the control line is weak or very weak.