Limitations
While the Kastle-Meyer test has been reported as being able to detect blood dilutions down to 1:107, there are a number of important limitations to the test. The test will give a false positive result when in the presence of vegetable peroxidases, such as those in horseradish, broccoli, cauliflower, etc. Additionally, other oxidizing species in the sample will also cause a false positive. 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.
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.
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 positive can be generated in the presence of a reducing agent.
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