Evaluation of sensitivity and specificity of routine meat inspection of Danish slaughter pigs using Latent Class Analysis

Two groups of observers, regular meat inspectors and two veterinary researchers, respectively, conducted independent veterinary meat inspection of organs of slaughter pigs from organic or conventional production systems slaughtered at one abattoir in April 2005. A total of 3054 pigs (899 organic and 2155 conventional) were examined. The observed pathological disorders were grouped in four categories; respiratory disorders (RESP), parasitic disorders (PAR), intestinal disorders (INT) and heart disorders (HEART). Using a latent class model, the sensitivity (Se) and specificity (Sp) of meat inspectors and researchers were estimated without the assumption of an available gold standard. The Se for the regular meat inspection was found to be 0.92, 0.16, 0.24 and 0.49 for RESP, PAR, INT and HEART, respectively. The Se for the researchers was found to be 0.81, 0.96, 0.91 and 0.68 for RESP, PAR, INT and HEART, respectively. The Sp for the regular meat inspection was found to be between 0.98 and 1.00 for the four categories. The Sp for the researchers was found to be 0.83, 0.94, 0.76 and 0.99 for RESP, PAR, INT and HEART, respectively. The low Se of ordinary meat inspection for parasitic, intestinal and heart disorders will cause a significant underestimation of the prevalence of diseases reported to the pig producers. Based on our results the true prevalence of diseases (conventional vs. organic slaughter pigs) was (in %): 42 vs. 16, 5 vs. 51, 5 vs. 12 and 9 vs. 5 for RESP, PAR, INT and HEART, respectively.