<P> Optionally, the swab can first be treated with a drop of ethanol in order to lyse the cells present and gain increased sensitivity and specificity . This test is nondestructive to the sample, which can be kept and used in further tests at the lab; however, few labs would use the swab used for the Kastle--Meyer test in any further testing, opting instead to use a fresh swab of the original stain . </P> <P> While the Kastle--Meyer test has been reported as being able to detect blood dilutions down to 1: 10, there are a number of important limitations to the test . Chemical oxidants such as copper and nickel salts will cause the Kastle--Meyer reagent to turn pink before the addition of the hydrogen peroxide, thus it is vitally important to add the reagent first, then wait a few seconds, then add the hydrogen peroxide . </P> <P> The Kastle--Meyer test has the same reaction with human blood as it does with any other hemoglobin - based blood, so a confirmatory test such as the Ouchterlony Test must be performed to definitively conclude from which species the blood originated . </P> <P> Color catalytic tests are very sensitive, but not specific . The positive color test alone should not be interpreted as positive proof of blood . A negative result is generally proof of the absence of detectable quantities of heme, however a false negative can be generated in the presence of a reducing agent . </P>

What substances can cause a false positive kastle meyer test result