What is the purpose of a presumptive test for blood, and name a common example?

What is the purpose of a presumptive test for blood, and name a common example?

• A. To quantify the amount of blood present
• B. To indicate potential presence of blood and guide further testing; Kastle-Mauer test
• C. To identify the source individual from the stain
• D. To determine the age of the stain

Answer: (B)

Presumptive tests for blood are screening tools that quickly indicate whether blood might be present and help decide which follow-up tests to run. They aren’t meant to measure how much blood is there, identify who the donor is, or determine how old a stain is. A common example is the Kastle-Mauer test, which uses a color change driven by the peroxidase activity of hemoglobin. When blood is present, the reagent combination produces a pink color, signaling that further, more specific testing should be performed. Keep in mind these tests can give false positives with other peroxidase substances, and a negative result doesn’t completely rule out blood, so confirmatory analyses are needed.

Presumptive tests for blood are screening tools that quickly indicate whether blood might be present and help decide which follow-up tests to run. They aren’t meant to measure how much blood is there, identify who the donor is, or determine how old a stain is. A common example is the Kastle-Mauer test, which uses a color change driven by the peroxidase activity of hemoglobin. When blood is present, the reagent combination produces a pink color, signaling that further, more specific testing should be performed. Keep in mind these tests can give false positives with other peroxidase substances, and a negative result doesn’t completely rule out blood, so confirmatory analyses are needed.