Atypical Pleural Fluid Profiles in Tuberculous Pleural Effusion: Sequential Changes Compared with Parapneumonic and Malignant Pleural Effusions.

Objective Although tuberculous pleural effusion (TPE) is commonly characterized by lymphocytic predominance and high adenosine deaminase (ADA) levels, it may present with neutrophilic predominance or low ADA levels, which are more commonly found in parapneumonic effusion (PPE) or malignant pleural effusion (MPE), respectively. A few studies have observed that the atypical pleural fluid profiles of these cases of TPE may resolve at follow-up thoracentesis. However, these observations were incompletely analyzed and lacked comparison with proper control groups. Thus, limited data are available comparing the sequential pleural fluid changes between TPE and PPE or MPE with similar pleural fluid profiles. Methods TPE, PPE, and MPE patients who underwent sequential thoracentesis were retrospectively reviewed. The sequential changes in the pleural fluid profiles were compared between neutrophilic TPE and PPE, and lymphocytic TPE and MPE with low ADA levels. Results Twenty-three TPE patients (16 with neutrophilic exudates, seven with lymphocytic exudates), 72 cases of PPE with neutrophilic exudates, and 18 cases of MPE with lymphocytic exudates were included in the analysis. A sequential shift to lymphocytic exudates occurred significantly more often in TPE than in PPE cases. The initial and follow-up ADA levels in TPE cases with a lymphocytic shift were significantly higher than those in PPE cases with a lymphocytic shift. The ADA levels in the TPE cases with initial lymphocytic exudates and low ADA levels significantly increased at follow-up thoracentesis. For the TPE and MPE cases with initial lymphocytic exudates and ADA levels <40 U/L, the frequency of effusion with ADA levels ≥40 U/L at the second thoracentesis was significantly higher in the TPE cases. Conclusion Follow-up thoracentesis may provide useful information for clinical decision-making in suspected atypical TPE cases with neutrophilic exudates or low ADA levels.