Comparison of Some Indirect Screening Tests for Detection of Subclinical Mastitis in Dairy Cows

A total of 335 quarter milk samples from crossbred dairy cows were subjected to California mastitis (CMT), sodium lauryl sulphate (SLST), and somatic cell count (SCC) tests. CMT positive milk samples were 227, while 108 samples were CMT negative. Milk samples positive by SLST and SCC were 261 and 180 respectively. The CMT positive samples were subjected to cultural isolation (gold standard test for comparison of indirect mastitis tests). Of these, 201 samples were positive by cultural isolation. The sensitivity of the CMT, SLST and SCC was 86.07%, 74.63% and 88.60%; specificity 59.70%, 17.16% and 97.76%; percentage accuracy 75.52%, 51.64% and 91.94%; positive predictive value 76.21%, 57.47% and 98.33%; and negative predictive value 74.07%, 31.08% and 84.52%, respectively. Kappa value of SCC was higher than that of CMT. CMT was concluded to be the most accurate test after cultural isolation and SCC. Unlike laboratory tests as cultural isolation and SCC that require adequate laboratory facilities and skilled personnel, CMT is a reliable diagnostic method in field conditions.