it指代什么？谢谢

Chylothorax, pseudochylothorax and empyema can be distinguished by the following criteria. Firstly, by physical appearance: the classical appearance of a chylothorax is of a milky, opalescent fluid in 50% of cases [6]. However, this is sometimes unreliable since if the patient has been fasting this may be clear, and in traumatic cases it may be bloody [3]. Secondly, by biochemical criteria: a triglyceride level >110 mg/dL, cholesterol level <200 mg/dL 50% of cases [3] are exudative i.e. high protein and low lactate dehydrogenase. If the effusion is transudative this may indicate an underlying hepatic or cardiac cause, for example, cirrhosis [5]. Lastly, by fluid analysis, which is the definitive test. Presence of chylomicrons, small particles made up of long chains of triglycerides, is diagnostic as these are absorbed directly into and transported by the lymphatic system. These lipids can be detected with Sudan staining but this technique should be supported with fluid analysis as it has a low specificity [4]. Currently there are no quantitative criteria for diagnosis. If chylomicron testing is not available, triglycerides quantification can be used to aid identification. A pseudochylothorax is an effusion that may appear similar to chylothorax but does not fulfil the biochemical criteria. It is the result of a chronic effusion that may develop over months to years, which can be distinguished by its high cholesterol content. The defining criteria is a cholesterol >200 mg/dL with triglyceride <50 mg/dL but it can be > 1000 mg/dL [5]. The origin of the cholesterol is thought to be through the continued breakdown of inflammatory cells in a chronic effusion. 54% are caused by tuberculous effusions [5]. Other causes include rheumatoid pleurisy, trapped lung syndrome and partially drained empyemas. The milky appearance of pseudochyle will also disappear on addition of ethyl ether-another method of distinguishing from chyle [4]. In addition to clinical history and examination, chylothorax can be differentiated from empyema with centrifugation. Chyle will remain uniform after being processed whereas empyema will form a supernatant [4].

通过以下标准可区分乳糜胸、假性乳糜胸和脓胸。首先，外观：50%的乳糜胸病例胸腔积液的典型外观为乳白色液体^[6]。然而，外观有时不可靠，因为若患者禁食，胸腔积液可能是清亮的，而创伤时可能是血性的^[3]。其次，根据生化标准：乳糜胸病例胸腔积液的甘油三酯水平>110 mg/dL，胆固醇水平< 200 mg/dL，50%是渗出性积液（即高蛋白和低乳酸脱氢酶）^[3]。如果积液是漏出性的，可能提示潜在的肝脏或心脏病因，如肝硬化^[5]。最后，胸腔积液的成分分析可确诊，因乳糜微粒（由甘油三酯长链组成的小颗粒）被淋巴系统直接吸收和转运，若胸腔积液检出乳糜微粒（可以通过苏丹染色检测）则具有诊断意义，但苏丹染色只是识别脂质，对乳糜微粒检测的特异性较低，故其对胸腔积液性质的识别还应得到积液其他分析的支持^[4]，目前尚无诊断的定量标准。若不能检测乳糜微粒，则甘油三酯定量可资辩别。假性乳糜胸是一种外观与乳糜胸相似但生化标准不符的慢性积液，可有数月至数年的病史，可通过其高胆固醇含量（定义标准为胆固醇>200 mg/dL且甘油三酯<50 mg/dL，有时胆固醇可高达>1000 mg/dL）与乳糜胸鉴别^[5]，胆固醇认为是由慢性积液中炎性细胞的持续分解而来。54%的假性乳糜胸由结核性积液引起^[5]，其他病因包括类风湿胸膜炎、闭锁肺综合征和部分引流后脓胸。另一种识别乳糜胸的方法是加入乙醚，假乳糜胸乳糜液的乳状外观在加入乙醚后会消失^[4]。除病史及检查，可通过离心乳糜液将乳糜胸与脓胸判别，离心后乳糜胸水仍均匀，而脓胸液将形成上清液^[4]。

it 指代什么？是Sudan staining还是乳糜微粒？

this technique should be supported with fluid analysis as it has a low specificity 但苏丹染色只是识别脂质，对乳糜微粒检测的特异性较低，故其对胸腔积液性质的识别还应得到积液其他分析的支持 理解的对吗？

谢谢