Comparison of sensitivity and specificity of somatic cell count and identification of milk amyloid A concentration by a sandwich-ELISA for diagnostic purpose of acute, subclinical and chronic mastitis in dairy cows

The project focusses on a new method for mastitis diagnostic in dairy cows. At the moment, the diagnostic is based on the following three test procedures:

1. California Mastitis Test (CMT): Used as a screening test at cowsheds, gives a rough impression about the somatic cell count.
2. Somatic cell counter (SCC): machine counting somatic cells (Leukocyte, macrophages, lymphocytes, erythrocytes, epithelial cells) in milk samples automatically.
3. Bacteriological culture: aetiological diagnose by identification of the bacteria out of the milk sample.

Unfortunately, there is poor or even no correlation between SCC/CMT and the results of bacteriological culture. Cows can have very high somatic cell count with only low or without any bacteriological infection of the udder and vice versa. Thus, somatic cell count is an improperly and unreliable predictor for the udder health and it’d be beneficial to develop a new diagnostic procedure with higher sensitivity and specificity for mastitis diagnostic in veterinary medicine.

It is possible to measure the concentration of acute phase proteins in milk, such as the milk amyloid A (MAA) with a sandwich ELISA. Concentration of acute phase proteins, in milk or serum, increase very fast after infection and decrease fast during successful therapy, too.

The goal of this thesis is to determine the sensitivity and specificity of the MAA-ELISA in mastitis diagnostic by using latent class analysis, because there is no gold-standard. By comparing the four tests, MAA-ELISA, CMT, SCC and bacteriological culture, we want to investigate which is the best marker for mastitis.

The results have been published in the Journal of Dairy Science: https://doi.org/10.3168/jds.2016-12446