From UpToDate: Tuberculous pleural effusions
http://www.uptodate.com/online/content/topic.do?topicKey=tubercul/4487&selectedTitle=1%7E21&source=search_result
Special tests — Several special tests, such as pleural fluid adenosine deaminase and lysozyme concentrations, have been investigated for use in diagnosing tuberculous pleural effusions.
None are routinely used at present.
->許多特殊的檢查可以幫忙診斷TB性胸水。可惜的是，沒有任何一種被當作routine檢查。
Adenosine deaminase — Pleural fluid adenosine deaminase (ADA) concentrations are elevated in tuberculous pleural effusions. Some large series suggest that ADA is 100 percent sensitive and 95 to 97 percent specific when a value
above 45 to 60 U/L is found. However, one report found levels above 43 U/L in only 68 of 87 cases (78 percent sensitivity), while other series found specificities in the range of 85 to 89 percent.
->胸水中腺嘌呤去胺脢(ADA)濃度在TB性胸水中會升高。許多研究指出當濃度超過 45 to 60 U/L，其 診斷sensitivity達100% ，specificity達 95 to 97 %。不過有些報告說specificity其實只有78%或85-89%。
Specificity is decreased by high ADA levels that occasionally occur in other conditions, including rheumatoid effusion, empyema, mesothelioma, lung cancer, parapneumonic effusion, and hematologic malignancies. Choosing a lower ADA cutoff value will increase sensitivity at the expense of specificity. However, pleural effusions with an ADA level below 40 U/L are rarely caused by tuberculosis
.
-> 偶而會遇到類風濕性胸水.膿胸.間皮癌.肺癌.肺炎性胸水和血液腫瘤等原因引起的胸水，其ADA濃度也會上升，因此會降低ADA診斷TB性胸水的specificity。胸水ADA濃度如果小於40U/L，很少是因為TB引起的。
These variable findings may in part reflect failure to distinguish between the two principal isoenzymes, ADA-1 and ADA-2. ADA-2 is increased in tuberculous effusions, while ADA-1 rises in empyemas. Most studies have reported only the total ADA level.
-> ADA-2在tuberculous effusions會升高，ADA-1在epmyema會升高。不過大部分的實驗都是設計測定total ADA level。
At present, pleural fluid ADA remains "an aid to differential diagnosis," as it was originally described in 1978 . It is most useful in the 10 percent of patients with tuberculous pleurisy who have negative standard diagnostic studies, ie, negative pleural histology and culture.
->從1978年被發現以來，目前胸水ADA濃度的角色仍當作是"an aid to differential diagnosis"。它最有用的地方在於幫忙診斷有10%TB胸水的病人，而其胸水的 histology and culture都是陰性時。
