The objective of this study was to compare the performance of different diagnostic tests for the detection of pigs subclinically infected with Actinobacillus pleuropneumoniae. To address this question, we infected pigs with APP serotypes 1, 3, 5, 7, 10, 12, and 15 and collected weekly tonsil swabs for isolation and PCR and serum samples for serological testing. Our results showed that the Multi-APP ELISA test tended to detect infection one week earlier than the serotype-specific ELISA tests. The Multi-APP ELISA was also more consistent in identifying positives throughout the experiment. This is the first study to compare different diagnostic tests for the detection of subclinical infected pigs with APP serotypes clinically relevant to the U.S. swine industry. We recommend the use of the Multi-APP ELISA test for serological screening followed by testing of positive serum samples with the serotype-specific ELISA test offered by BIOVET.