Martin S W, Bonnett B
Can Vet J. 1987 Jun;28(6):318-25.
Rational clinical practice requires deductive particularization of diagnostic findings, prognoses, and therapeutic responses from groups of animals (herds) to the individual animal (herd) under consideration This process utilizes concepts, skills, and methods of epidemiology, as they relate to the study of the distribution and determinants of health and disease in populations, and casts them in a clinical perspective.We briefly outline diagnostic strategies and introduce a measure of agreement, called kappa, between clinical diagnoses. This statistic is useful not only as a measure of diagnostic accuracy, but also as a means of quantifying and understanding disagreement between diagnosticians. It is disconcerting to many, clinicians included, that given a general deficit of data on sensitivity and specificity, the level of agreement between many clinical diagnoses is only moderate at best with kappa values of 0.3 to 0.6.Sensitivity, specificity, pretest odds, and posttest probability of disease are defined and related to the interpretation of clinical findings and ancillary diagnostic test results. An understanding of these features and how they relate to ruling-in or ruling-out a diagnosis, or minimizzing diagnostic errors will greatly enhance the diagnostic accuracy of the practitioner, and reduce the frequency of clinical disagreement. The approach of running multiple tests on every patient is not only wasteful and expensive, it is unlikely to improve the ability of the clinician to establish the correct diagnosis.We conclude with a discussion of how to decide on the best therapy, a discussion which centers on, and outlines the key features of, the well designed clinical trial. Like a diagnosis, the results from a clinical trial may not always be definitive, nonetheless it is the best available method of gleaning information about treatment efficacy.
合理的临床实践需要将从动物群体（畜群）得出的诊断结果、预后和治疗反应，演绎性地细化到所考虑的个体动物（畜群）。这个过程运用了流行病学的概念、技能和方法，因为它们与人群中健康和疾病的分布及决定因素研究相关，并从临床角度加以应用。我们简要概述诊断策略，并介绍一种临床诊断之间的一致性度量方法，称为kappa值。这个统计量不仅可作为诊断准确性的度量，还可作为量化和理解诊断者之间分歧的一种手段。令包括临床医生在内的许多人感到不安的是，鉴于关于敏感性和特异性的数据普遍不足，许多临床诊断之间的一致性水平充其量也只是中等，kappa值在0.3至0.6之间。定义了疾病的敏感性、特异性、验前概率和验后概率，并将它们与临床发现及辅助诊断测试结果的解释相关联。理解这些特征以及它们与确诊或排除诊断的关系，或者最小化诊断错误，将极大提高从业者的诊断准确性，并减少临床分歧的频率。对每个患者进行多项测试的方法不仅浪费且昂贵，而且不太可能提高临床医生做出正确诊断的能力。我们最后讨论如何确定最佳治疗方案，该讨论围绕精心设计的临床试验的关键特征展开并进行了概述。与诊断一样，临床试验的结果可能并不总是确定的，但它是获取有关治疗效果信息的最佳可用方法。
