Sumon S M Mostafizur Rahaman, Parvin Mst Sonia, Ehsan Md Amimul, Islam Md Taohidul
Population Medicine and AMR Laboratory, Department of Medicine, Faculty of Veterinary Science, Bangladesh Agricultural University, Mymensingh 2202, Bangladesh.
Department of Medicine, Faculty of Veterinary Medicine and Animal Science, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur 1706, Bangladesh.
Vet World. 2020 Aug;13(8):1709-1713. doi: 10.14202/vetworld.2020.1709-1713. Epub 2020 Aug 27.
Subclinical mastitis (SCM) is one of the most prevalent diseases of dairy cows, and somatic cell count (SCC) is widely used to determine SCM and milk quality. However, setting the threshold of SCC is very important. This study aimed to determine the cow-level threshold of SCC to differentiate milk of SCM affected cows from normal milk in Bangladesh.
Sensitivity (Se) and specificity (Sp) along with other characteristics of different thresholds of SCC were determined considering the bacterial culture as the gold standard test. Three definitions of intramammary infection (IMI) were set based on the group of pathogens involved. Five categories of SCC thresholds were considered for analysis.
Se and Sp of thresholds of SCC greatly varied as definitions of IMI changed. Irrespective of SCC thresholds, Se increased when isolation of major pathogens included in IMI definitions. Se decreased when SCC thresholds increased (from 100 to 300 × 10 cells/mL) for all IMI definitions and ranged from 60.6% to 20.3%. The highest Se was found at low SCC threshold (100 × 10 cells/mL), which resulted in less false-negative outcome. On the other hand, Sp increased with the increment of SCC thresholds giving rise to a less false-positive outcome.
The cow-level SCC threshold of 100 × 10 cells/mL was found appropriate to identify subclinical IMI of dairy cows.
亚临床型乳腺炎（SCM）是奶牛最常见的疾病之一，体细胞计数（SCC）被广泛用于判定SCM和牛奶质量。然而，设定SCC的阈值非常重要。本研究旨在确定孟加拉国奶牛水平的SCC阈值，以区分受SCM影响奶牛的牛奶与正常牛奶。
以细菌培养作为金标准检测，确定SCC不同阈值的敏感性（Se）和特异性（Sp）以及其他特征。基于所涉及的病原体组设定了三种乳房内感染（IMI）的定义。分析时考虑了五类SCC阈值。
随着IMI定义的变化，SCC阈值的Se和Sp差异很大。无论SCC阈值如何，当IMI定义中包括主要病原体的分离时，Se会增加。对于所有IMI定义，当SCC阈值增加（从100×10⁴到300×10⁴细胞/mL）时，Se会降低，范围从60.6%到20.3%。在低SCC阈值（100×10⁴细胞/mL）时发现Se最高，这导致假阴性结果较少。另一方面，Sp随着SCC阈值的增加而增加，从而产生较少的假阳性结果。
发现100×10⁴细胞/mL的奶牛水平SCC阈值适合识别奶牛的亚临床IMI。
