Lesions of swine lymph nodes as a diagnostic test to determine mycobacterial infection

Decisions as to the disposition of swine carcasses with lesions attributable to a mycobacterial infection are based upon a lesion criterion which is used as a diagnostic test by federal meat inspectors. Using this criterion, a federal meat inspector classified 58 of 100 pigs as "passed for cooking" and the other 42 pigs passed. Of the 58 pigs passed for cooking and the 42 pigs passed, mycobacterial isolations were made from the lymph nodes of 33 and 15 of the animals, respectively. The lesion criterion as a diagnostic test has the following attributes: 70% sensitive; 53% specific; 23% index of performance; 57% positive accuracy; and 67% negative accuracy.