From the Guidelines
Laboratory tests for thoracentesis should include pleural fluid analysis for cell count and differential, protein, lactate dehydrogenase (LDH), glucose, pH, Gram stain, culture, and cytology, as these tests help differentiate between transudative and exudative effusions and guide treatment decisions. When considering malignancy, it is reasonable to order the following pleural fluid tests: nucleated cell count and differential, total protein, lactate dehydrogenase (LDH), glucose, pH, amylase, and cytology 1. Additional tests may be ordered based on clinical suspicion, such as:
- Adenosine deaminase (ADA) for tuberculosis
- Amylase for pancreatic disease or esophageal rupture
- Triglycerides for chylothorax
- Tumor markers for malignancy Prior to the procedure, coagulation studies (PT/INR, PTT, platelet count) should be checked to assess bleeding risk, especially in patients on anticoagulants or with liver disease 1. A complete blood count and basic metabolic panel are also recommended to evaluate for infection and assess kidney function. Post-procedure, a chest X-ray is typically performed to rule out pneumothorax, and ultrasound-guided thoracentesis is recommended to improve the success rate and decrease the rate of pneumothorax 1. If pleural fluid cytology is negative, pleural biopsy (via image-guided pleural biopsy, medical or surgical thoracoscopy) is recommended as the next step 1. It is also important to note that a second thoracentesis may be considered before proceeding to biopsy of the pleura if pleural cytology is negative after the first thoracentesis 1.
From the Research
Pre-Procedural Labs for Thoracocentesis
- The study 2 found that moderate coagulopathies (international normalized ratio less than 3 or a platelet count greater than 25,000/μL) did not increase the risk of postprocedural complications, suggesting that coagulation studies such as INR and platelet count may be relevant labs to consider before thoracocentesis.
- Complete blood count (CBC) components, including platelet count, are discussed in studies 3 and 4, highlighting their importance in understanding various medical conditions, but they do not specifically address the necessity of these labs for thoracocentesis.
Relevant Labs
- Platelet count: mentioned in study 2 as a factor to consider before thoracocentesis, with a count greater than 25,000/μL not increasing the risk of complications.
- International normalized ratio (INR): also mentioned in study 2 as a factor, with an INR less than 3 not increasing the risk of complications.
- Complete blood count (CBC): while not directly related to thoracocentesis in studies 3 and 4, it provides valuable information on various cell components, including platelet count.