Reliability of the California Mastitis Test and electrical conductivity for mastitis diagnosis in Mediterranean Buffaloes (Bubalus bubalis)

: The observational prospective study assesses the clinical utility of the California Mastitis Test (CMT) and electrical conductivity (EC) for mastitis diagnosis in Mediterranean buffaloes, for the first time. A total of 600 quarter-milk samples were aseptically collected from randomly selected, multiparous Mediterranean buffaloes. All samples were submitted to the reference laboratory for SCC and bacteriological milk culture (BMC), which served as the gold standard (GS), whereas the CMT and EC were recorded and performed on-farm immediately after milking. Based on the GS results, quarters were classified as mastitis cases when an inflammatory response (SCC > 200 × 103 cells/mL) was associated with a bacteriological positivity with or without obvious clinical signs. Quarters without concurrent inflammatory response were classified as nonmastitis cases, regardless of bacteriological findings. For the validation both EC and CMT were compared with SCC as the benchmark test. Thereafter, CMT and EC were compared with the GS to assess their ability to correctly identify udder health status both independently and associated with BMC as potential alternatives to the use of SCC in field. Overall, 134 mastitis cases and 466 nonmastitis cases were detected. For the diagnostic validation (CMT and EC vs. SCC) the Cohen's kappa revealed a significant n agreement of 0.51 and 0.27 for CMT and EC, respectively. An area under the receiver operating characteristic curve (AUC) of 0.97 for CMT and 0.75 for EC was calculated, with accuracy values of 0.76 for CMT and 0.73 for EC. Sensitivity (Se) was 0.97 for CMT and 0.45 for EC, and specificity (Sp) was 0.69 for CMT and 0.82 for EC. The positive likelihood ratio (LR+) was 3.15 for CMT and 2.45 for EC, and the negative likelihood ratio (LR-) was 0.04 for CMT and 0.68 for EC. When both tests were compared with the GS (CMT and EC vs. GS), the Se was 0.97 for CMT and 0.46 for EC, whereas the Sp was 0.67 for CMT and 0.81 for EC, with accuracies of 0.74 for CMT and 0.73 for EC were detected. The LR+ values were 2.92 for CMT and 2.41 for EC, with LR- values of 0.04 for CMT and 0.67 for EC. Finally, when both the tests were combined with BMC (CMT+BMC and EC+BMC vs. GS), The sensitivity was 0.97 for CMT and 0.46 for EC, and specificity was 0.74 for CMT and 0.89 for EC, with an accuracy of 0.79 for both tests were observed. The LR+ was 3.77 for CMT and 4.00 for EC, and LR- values were 0.04 for CMT and 0.61 for EC. The CMT demonstrated better performance as diagnostic tools for mastitis cases, with a higher AUC and sensitivity, as compared with EC. In contrast, the latter seems to be useful for confirming the absence of mastitis due to its high-er specificity. Neither test alone should be relied upon for definitive diagnosis; a combination with BMC seems to improve their diagnostic performance, but CMT consistently outperformed EC.