Department of Cellular Pathology, Royal Free London NHS Foundation Trust, London, UK.
Liver Int. 2013 Jul;33(6):926-35. doi: 10.1111/liv.12162. Epub 2013 Apr 7.
BACKGROUND & AIMS: Evaluate in liver biopsies: (i) interobserver agreement of estimates of fat proportionate area (eFPA) and steatosis grading, (ii) the relationship between steatosis grades and measured fat proportionate area (mFPA, digital image analysis), (iii) the accuracy of eFPA, (iv) to present images to aid standardization and accuracy of eFPA.
Twenty-one liver biopsies were selected from the Royal Free Hospital (RFH) histopathology archive to represent the full range of histopathological steatosis severity. As many non-overlapping fields of parenchyma as possible were photographed at ×20 objective magnification from the biopsies (n = 651). A total of 15 sample images were selected to represent the range of steatosis seen. Twelve hepatopathologists from 11 sites worldwide independently evaluated the sample images for steatosis grade [normal (none)/mild/moderate/severe], and eFPA (% area of liver parenchyma occupied by fat).
The hepatopathologists had good linear correlation between eFPA and mFPA for sample images (r = 0.924, P < .001) and excellent concordance (kappa = 0.91, P < 0.001). Interobserver concordance of steatosis grade showed 'substantial agreement' (kappa = 0.64). There was significant difference between eFPA and mFPA in the sample images for mild, moderate and severe steatosis (P = 0.024, P < 0.001, P < 0.001 respectively): the observers consistently over-estimated the eFPA.
Hepatopathologists showed 'excellent' interobserver agreement in eFPA and 'substantial' agreement in assigning steatosis grade (precision was high). However, compared with mFPA, eFPA was inaccurate. eFPA systematically exceeds mFPA; generally the overestimation increases with severity of steatosis. Considering that non-invasive technologies for estimating liver fat utilize histopathology as reference, such assessments would benefit from quantitative validation of visually estimated microscopic liver fat percentages.
评估肝活检：（i）脂肪比例面积（eFPA）估计和脂肪变性分级的观察者间一致性，（ii）脂肪变性分级与测量脂肪比例面积（mFPA，数字图像分析）之间的关系，（iii）eFPA 的准确性，（iv）提供图像以帮助标准化和提高 eFPA 的准确性。
从皇家自由医院（RFH）组织病理学档案中选择 21 例肝活检组织，以代表组织病理学脂肪变性严重程度的全范围。尽可能从活检组织中以×20 物镜拍摄尽可能多的非重叠实质区域（n = 651）。共选择 15 个样本图像来代表观察到的脂肪变性范围。来自全球 11 个地点的 12 位肝脏病理学家独立评估样本图像的脂肪变性分级[正常（无）/轻度/中度/重度]和 eFPA（脂肪占据肝实质的百分比面积）。
肝脏病理学家在样本图像的 eFPA 和 mFPA 之间具有良好的线性相关性（r = 0.924，P < 0.001），并且具有极好的一致性（kappa = 0.91，P < 0.001）。脂肪变性分级的观察者间一致性显示“高度一致”（kappa = 0.64）。在轻度、中度和重度脂肪变性的样本图像中，eFPA 和 mFPA 之间存在显著差异（P = 0.024，P < 0.001，P < 0.001 分别）：观察者一致高估了 eFPA。
肝脏病理学家在 eFPA 方面表现出“出色”的观察者间一致性，在脂肪变性分级方面表现出“实质性”的一致性（精度高）。然而，与 mFPA 相比，eFPA 并不准确。eFPA 系统地超过 mFPA；通常，随着脂肪变性的严重程度增加，高估的程度也会增加。鉴于用于估计肝脂肪的非侵入性技术利用组织病理学作为参考，因此此类评估将受益于对视觉估计的微观肝脂肪百分比进行定量验证。
