Sensitivity and Detection Efficiency of the Peroxidase Antiperoxidase (PAP), Avidin-biotin Peroxidase Complex (ABC), and Peroxidase-labeled Avidin-biotin (LAB) Methods

The authors have examined the sensitivity and detection efficiency of the three peroxidase methods that currently have the widest application in diagnostic immunohistochemistry: the peroxidase-antiperoxidase (PAP), the avidin-biotin complex (ABC), and the labeled avidin-biotin (LAB) methods. Sensitivity was evaluated by determining the highest useful dilution of polyclonal antiglucagon antibodies applied to formalin-fixed, paraffin-embedded human pancreas. Detection efficiency was evaluated by tabulation of the total number of positive (three or more positive cells) islets. On direct comparison, the LAB method exceeded the PAP and ABC methods in both sensitivity and detection efficiency, which were essentially equal. Titration of linking antiserum of the PAP method boosted its sensitivity and detection efficiency above that of ABC; the PAP had equal sensitivity to the LAB and exceeded it in detection efficiency. The authors conclude that comparisons of immunohistologic methods are meaningful only if both sensitivity and efficiency are considered along with the unique requirements of any single method.