血小板相关文章

康奈尔大学兽医学院

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哺乳动物血小板（或凝血细胞）是包含粉色至红色小颗粒的无核细胞，由骨髓中巨核细胞释放入血，在凝血过程中起重要作用。虽然大多血小板比红细胞小，但例外情况在犬猫也并不罕见。

正常的血小板形态和物种差异

不同物种的血小板大小差异较大，所有动物都可能见到较大的血小板。血小板体积变化和血小板分布宽度都可经血液分析仪测量。这和红细胞分布宽度测量方法和计算方法类似（血小板标准偏差÷平均血小板体积）。这个血小板检测指标通常不列在报告里，但平均血小板体积和血小板计数及血涂片上血小板计数在大多数血象报告上都包括。大号血小板通常被认为是不成熟的血小板，但尺寸和不成熟并不是一回事。一些不成熟血小板会很小，而大号血小板可以通过多种机制产生，如巨核细胞的血小板生成异常。

血小板细胞质中也含有粉色颗粒，一些物种中这些小颗粒很难识别，比如马。任何原因引起的血小板激活（血小板脱颗粒）或血小板吸水都可使血小板颗粒缺失。某些基于激光的血液分析仪，可测量血小板的内部复杂性（颗粒度），这个指标是平均血小板成分浓度（MPC），类似于基于激光测量的红细胞血红蛋白浓度（细胞血红蛋白[CH]和平均红细胞血红蛋白浓度[CHCM]）。只有在分析仪内将血小板做适当的球形化处理，才能够得到精确的平均血小板成分。

血小板通常呈球形或椭圆形，但在一些动物也可见细长形或纺锤形。血样中有轻度激活或接触载玻片（猫血样很常见）的血小板可能呈现树枝状星型结构（见下面图片）。

下面是不同家养动物的血小板

犬

犬血小板大小变化范围较小，血小板颗粒着色良好。这一区域是血涂片“红细胞区”的一个很好代表。应该利用该区域评估血小板计数。

犬血小板分散在血涂片的单细胞层。颜色由红色至粉色，大小略有变化。

猫

猫血小板大小差异范围比犬大，在非疾病状态或健康猫血液中也可以见到很多大号血小板。猫血液样本采集过程中血小板很容易被激活并经常凝集，影响血小板精确计数。最好的避免避免血小板凝集的方法即洁净的静脉穿刺操作和稳定采血及血样搅拌程度最低。当然即便是最佳的准备和技术，也还是会出现血小板凝集。

猫血涂片可见几个大号血小板和含有树枝状突起的血小板。这种程度的血小板尺寸变化对于猫是正常的。右下角是一个大号血小板。

马 

马的血小板通常在大小和外形上都保持一致。血小板颗粒在常规血液学染色方法中着色很浅，使得血小板外观苍白，有时低倍镜很难发现。马的血小板计数通常低于其他动物。

马血小板一般是圆形且比其他动物颜色更浅（马血小板也有颗粒，只是更难辨别）。马血小板数量也少于其他动物（正常参考范围的下限值是94,000/uL；这个指标在其他动物已经可以认为轻度的血小板减少症）。

英语原文

Platelets (or thrombocytes) in mammals are anucleate cells that contain small pink-red granules. Shed into the blood from megakaryocytes in bone marrow, they are key players in the hemostatic process. Though most platelets are smaller than red cells, exceptions to this are not uncommon in cats and dogs.

Platelets tend to very in size in all species, with some large platelets being seen in all species. The variation in platelet volume is measured on hematologic analyzers as the platelet distribution width. This is analogous to the red blood cell distribution width and is calculated similarly (standard deviation of platelet volume ÷ mean platelet volume). This platelet test result is not usually reported, but the mean platelet volume is reported on most hemograms, along with the platelet count and a smear assessment of platelet numbers. Large platelets are often considered immature platelets, however size and immaturity are not synonymous. Some immature platelets are small and large platelets can form through other mechanisms, e.g. abnormalities in platelet production by the megakaryocyte.

Platelets also have pink granules in their cytoplasm. The granules are less discernible in some species, such as the horse. Loss of granulation can be seen if platelets become activated for any reason (platelets de-granulate) or if they imbibe water. Laser-based hematology analyzers, such as the ADVIA 2120, can provide a measurement of the internal complexity (granularity) of the platelet, as the mean platelet component (MPC). This is analogous to laser-based measurement of hemoglobin concentration (cellular hemoglobin [CH] and corpuscular hemoglobin concentration mean [CHCM]) in red blood cells. Accurate values for the mean platelet component  are only obtainable if platelets are sphered adequately in the analyzer.

Platelets are generally round to oval, however elongated and spindled forms can be seen in some animals. Platelets that have been slightly activated in the sample or by contact with the glass slide (as is common in feline samples) can have a stellate form with dendritic processes (see figure of the cat platelets below).

Comments on platelets in the different domestic species are given below.

Canine platelets Platelets are dispersed in the monolayer of a canine blood film. They have red to pink granules and vary somewhat in size.

Canine platelets are moderately variable in size; platelet granules are well-stained. This field is a good representation of the “red cell area” of the smear. It is in this area that the estimate of platelet numbers should be made.

Feline

Several large platelets and platelets with dendritic processes (possibly activated) are seen in the blood smear from this cat. This degree of variation in platelet size is normal for this species. The inset shows a large platelet.

Cat platelets tend to vary more in size than dogs, with many large platelets being seen in blood from non-diseased or healthy cats. Platelets are also readily activated on blood sample collection in cats and clump frequently, precluding accurate platelet counts in many individuals of this species. The best way to avoid platelet clumping is clean venipuncture and a steady blood draw, with minimal agitating of the sample. Despite best intentions and techniques, platelets can still clump.