Quality Control and Quality Assurance Procedures
Q: Which of the following factors is NOT listed in the SOP as something that can affect the accuracy of disc diffusion susceptibility results?
Did You Know?
This statement is true. The APAAP method was developed as a valuable alternative to peroxidase-based methods like PAP. Its major advantage is that it uses alkaline phosphatase (AP) as the label enzyme instead of horseradish peroxidase (HRP). Since many tissues (like blood, bone marrow, and inflammatory lesions) have high levels of endogenous peroxidase, using an HRP-based system requires careful and sometimes incomplete blocking. The APAAP method bypasses this problem entirely because tissues generally have very low levels of endogenous alkaline phosphatase, especially after formalin fixation. This results in much lower background and cleaner staining in such specimens. Additionally, the red reaction product from common AP chromogens (like Fast Red) provides excellent contrast and is useful for double-staining procedures in conjunction with a brown DAB (HRP) stain.
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