Tuberculous pleural effusion is characterised by all of the following features except effusion :
**Core Concept**
Tuberculous pleural effusion is a type of exudative pleural effusion caused by Mycobacterium tuberculosis infection. It is characterized by a complex interplay of chronic inflammation, fibrosis, and immune response. The pleural space is involved in the disease process, leading to the accumulation of fluid.
**Why the Correct Answer is Right**
Tuberculous pleural effusion typically presents with a high glucose level in the pleural fluid (usually > 60 mg/dL) due to the presence of high levels of lactate dehydrogenase (LDH) and other enzymes that metabolize glucose. This is in contrast to other types of exudative pleural effusions, which often have low glucose levels. The pleural fluid also typically has an elevated adenosine deaminase (ADA) level, which is a marker of cellular immune response.
**Why Each Wrong Option is Incorrect**
**Option A:** Low glucose levels in the pleural fluid are not characteristic of tuberculous pleural effusion, as they are more typically seen in other types of exudative pleural effusions, such as malignancy or rheumatoid arthritis.
**Option B:** Elevated ADA levels are not specific to tuberculous pleural effusion, as they can also be seen in other conditions with a cellular immune response, such as sarcoidosis or fungal infections.
**Option C:** High LDH levels in the pleural fluid are not specific to tuberculous pleural effusion, as they can also be seen in other types of exudative pleural effusions, such as malignancy or rheumatoid arthritis.
**Clinical Pearl / High-Yield Fact**
Remember that tuberculous pleural effusion is a type of exudative pleural effusion, and its diagnosis can be challenging. A high index of suspicion and a thorough clinical evaluation, including imaging studies and pleural fluid analysis, are essential for making an accurate diagnosis.
**Correct Answer:** D.