Tefferi Ayalew
Division of Hematology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA.
Curr Hematol Rep. 2005 May;4(3):213-7.
The total blood volume (BV) consists of the part occupied by red blood cells (RBC), which is referred to as red cell mass (RCM), and that occupied by plasma (ie, plasma volume). Quantitative laboratory measurements that are pertinent to RBC, including RBC count, hematocrit (Hct), and hemoglobin (Hgb) are expressed in reference to a given volume of whole blood and are therefore influenced by plasma volume. Consequently, a "direct" RCM measurement has been promoted as a more accurate indicator of the body's red cell content. In accordance with this view, an international group of investigators, then identified as the Polycythemia Vera Study Group (PVSG), recommended that RCM be measured and only if elevated should a patient be considered for participation in a series of clinical trials in PV that were conducted more than 30 years ago. By default, the 'study eligibility' criteria used in these studies became 'diagnostic' criteria without any systematic evaluation for diagnostic accuracy. Furthermore, over the years, it has become evident that RCM measurement is a cumbersome and costly test that is also suboptimal in its diagnostic accuracy. As a result, the specific procedure has been abandoned by the majority of hematologists in certain countries and instead physicians are increasingly using bone marrow histology, serum erythropoietin level, and other disease-characteristic biologic markers as diagnostic tools.
全血容量（BV）由红细胞（RBC）所占部分（称为红细胞量，RCM）和血浆所占部分（即血浆容量）组成。与红细胞相关的定量实验室检测指标，包括红细胞计数、血细胞比容（Hct）和血红蛋白（Hgb），均以给定体积的全血为参照进行表示，因此会受到血浆容量的影响。因此，“直接”测定红细胞量被认为是更准确反映机体红细胞含量的指标。按照这一观点，当时一个名为真性红细胞增多症研究组（PVSG）的国际研究团队建议测定红细胞量，只有当红细胞量升高时，患者才应考虑参与30多年前开展的一系列真性红细胞增多症（PV）临床试验。默认情况下，这些研究中使用的“研究入选”标准变成了“诊断”标准，却没有对诊断准确性进行任何系统评估。此外，多年来已明显看出，红细胞量测定是一项繁琐且昂贵的检测，其诊断准确性也欠佳。结果，某些国家的大多数血液学家已不再采用这一特定检测方法，转而越来越多地将骨髓组织学、血清促红细胞生成素水平及其他疾病特征性生物标志物用作诊断工具。
