Frequently Asked Questions

Q:  How accurate are they ?
A:  Test strips are comparable in accuracy to liquid color comparator tests. SteriChek Reagent Strips provide results by visual matching of a reagent strip to a calibrated color chart. This positive matching to the calibrated color chart does not have the error associated with other kits that require measuring sample volume, counting drops of reagent, etc.

Q:  What information supports the accuracy of test strips?
A:  SteriChek reagent strips are manufactured and released using standard reference procedures. For example, reagent strip results for chlorine are required to closely match results that are obtained when the same sample is analyzed utilizing a Standard Method of Analysis.

In addition, “blind studies” are conducted to verify the accuracy. A scientist prepares test samples at several different concentrations. People who are unaware of the actual concentrations are asked to assay the test samples with SteriChek reagent strips and report their results. The reported results must correlate with the actual concentrations in order for the product to be released for sale. This also ensures that the reagent strips are consistently reliable from bottle to bottle and lot to lot.

Q:  Is there anything that can affect the accuracy of the strips?
A:  There are factors that can affect the accuracy of reagent strips; however, they can be controlled. First, keep all unused strips in the original bottle. Do not remove the desiccant pack. Replace the cap immediately and tightly after removing a strip. Handle the strips with dry fingers to avoid introducing moisture into the bottle that would cause the reagent strips to react prematurely. Know the performance characteristics and limitations of the reagent strips. This information is generally provided with every complete kit. Finally, follow the directions provided for each test kit as they vary from manufacturer to manufacturer and may also change with product improvements.

Q:  Are there interferences that can affect the test results?
A:  Each test undergoes a complete check of potential interfering substances during product design and development. SteriChek strips are tested in the presence of several times the maximum limit of the chemical contaminants listed by AAMI to confirm the absence of interferences. Therefore, when water is maintained according to the AAMI standard, no potentially interfering substances will be present. Consult product inserts for limitations of individual SteriChek reagent strips.

Q:  Can values be determined that are not identical to the color block level?
A:  Yes. The sample being tested sometimes has a concentration that is not exactly the same as one of the concentration levels printed on the color chart. In such a case, the sample concentration is easily determined by interpolating between the nearest color blocks on either side of the activated reagent strip color.

Q:  What is the difference between residual chlorine, total chlorine and chloramines?
A:  Free residual chlorine is fresh chlorine that is still able to sanitize and oxidize contaminants in the water. When testing for residual chlorine in rinse water, this form of chlorine is being tested. Chloramine (combined chlorine) is chlorine that has combined with contaminants. Chloramines have very little sanitizing ability and are not effective oxidizing agents. However, chloramines are commonly used to treat municipal water supplies. In the enclosed system they can be useful to sanitize the water. Therefore, feed water that is not treated to remove these potential contaminants can contain low levels of chloramines. These chloramines also create an unpleasant, strong chlorine odor. Total chlorine includes both free residual chlorine and chloramines.

Q:  Why are there quality control methods to check performance of the reagent strips?
A:  A dialysis unit that implements routine quality control procedures using positive and negative controls will improve user proficiency, minimize procedural errors, and protect against the potential use of outdated or improperly stored or handled product. Each dialysis facility may choose to adopt the quality control method offered by the manufacturer, or it may choose to create its own. Consult the test kit insert for the quality control methods.


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