Title Rachel S, Harper Keith, Nelson Erik, Evans Tom, Tello Richard
Department of Radiology, Boston Medical Center, Boston University, Boston, MA 02118, USA.
AJR Am J Roentgenol. 2005 Nov;185(5):1240-4. doi: 10.2214/AJR.04.1171.
The purpose of this study was to evaluate the ability of expert reviewers to differentiate an anemic from a nonanemic state on the basis of visual assessment of the relative attenuation of blood in the left ventricle on noncontrast thoracic CT images and to compare reviewer performance with quantitative measurement of CT density in Hounsfield units.
One hundred two noncontrast thoracic CT examinations were qualitatively reviewed by three independent reviewers. Hounsfield unit measurements of the blood in the left ventricle were recorded by a fourth individual. Anemia was defined as a hemoglobin level of less than 10 g/dL. Receiver operating characteristic (ROC) analyses of expert reviewers were compared with measured Hounsfield units.
Hounsfield unit measurements performed significantly better than subjective reviewer analyses for differentiation of an anemic from a nonanemic state (area under ROC curve = 0.85 vs 0.72, 0.70, and 0.69; 95% confidence interval, 0.78-0.92 vs 0.63-0.81, 0.61-0.79, and 0.60-0.78, respectively; p < 0.05). With use of a CT density threshold of 35 H, the sensitivity for anemia was 76% and specificity was 81%, whereas the sensitivity of three reviewers was 40-72% with a specificity of 60-83%. Interobserver agreement was found to be poor by kappa statistic (0.0906-0.2128). The correlation coefficient for the analysis of Hounsfield unit versus hemoglobin level was 0.72. Separating data by patient sex revealed a correlation coefficient of 0.81 for men versus 0.52 for women, although the actual regression lines were not statistically different (p > 0.05).
Despite expert reviewer analyses, subjective evaluations of blood attenuation characteristics are prone to inaccuracy and show poor interobserver agreement. Quantitative measurements of CT density in Hounsfield units should be performed to accurately differentiate an anemic from a nonanemic state when serum hemoglobin levels are not readily available.
本研究旨在评估专家审阅者根据非增强胸部CT图像上左心室血液相对衰减的视觉评估来区分贫血状态与非贫血状态的能力，并将审阅者的表现与以亨氏单位进行的CT密度定量测量进行比较。
由三位独立审阅者对102例非增强胸部CT检查进行定性评估。由第四个人记录左心室血液的亨氏单位测量值。贫血定义为血红蛋白水平低于10 g/dL。将专家审阅者的受试者操作特征（ROC）分析与测得的亨氏单位进行比较。
在区分贫血状态与非贫血状态方面，亨氏单位测量的表现明显优于主观审阅者分析（ROC曲线下面积分别为0.85 vs 0.72、0.70和0.69；95%置信区间分别为0.78 - 0.92 vs 0.63 - 0.81、0.61 - 0.79和0.60 - 0.78；p < 0.05）。使用35 H的CT密度阈值时，贫血的敏感性为76%，特异性为81%，而三位审阅者的敏感性为40% - 72%，特异性为60% - 83%。通过kappa统计发现观察者间一致性较差（0.0906 - 0.2128）。亨氏单位与血红蛋白水平分析的相关系数为0.72。按患者性别分开数据显示，男性的相关系数为0.81，女性为0.52，尽管实际回归线在统计学上无差异（p > 0.05）。
尽管有专家审阅者分析，但对血液衰减特征的主观评估容易出现不准确情况，且观察者间一致性较差。当血清血红蛋白水平不易获取时，应以亨氏单位对CT密度进行定量测量，以准确区分贫血状态与非贫血状态。
