What is Pleural Fluid Analysis?

Laboratories classify the results of pleural fluid analysis into two types:

• Transudate pleural effusion: the result of an imbalance of pressure in certain blood vessels due to congestive heart failure or liver cirrhosis
• Exudate pleural effusion: the result of inflammation or injury to the pleura due to lung cancer, an autoimmune disorder, pneumonia, or a kidney condition

A doctor recommends pleural fluid analysis when he suspects pleural effusion. The symptoms for this are a dry, unproductive cough that doesn't go away, severe or constant chest pain, difficulty breathing, and fatigue. Sometimes people with pleural effusion have no symptoms. A doctor finds excess fluid in a chest X-ray conducted for other reasons.  

A healthcare professional removes pleural fluid from the pleura through a procedure known as thoracentesis. During this process:

• The patient sits on a chair or bed with arms resting on a table
• The doctor sanitizes the back and injects a numbing medicine
• The doctor inserts a needle between the ribs to withdraw fluid while the patient breathes out
• It results in the removal of excess fluid 

A medical study has revealed the pH of normal human pleural fluid at a value of 7.60-7.66. Transudate and exudate pleural effusions have a pH level of less than 7.30 but differ from condition to condition. To understand the specific meaning of test results, patients must seek the opinion of a healthcare professional.

Normal pleural fluid is clear yellowish and is between 10 - 20 ml in the human body. It contains a low protein concentration of fewer than 1.5 grams per deciliter (g/dL). Pleural fluid plays a key role in the physiological function of respiration in the human body. It helps diagnose, monitor, and assess certain medical conditions. 

A healthy human body contains 10-20 ml (about four tablespoons) of pleural fluid in the pleura. Other parameters are:

• Appearance: Clear, yellowish
• pH Balance: 7.60-7.66
• Protein: less than 1.5 d/dL
• Cholesterol: 3.5 - 6.5 mmol/L

Pathologists evaluate pleural fluid on overall appearance, pH level, microscopy, tumour markers, and other clinical data

The procedure of thoracentesis (taking a sample of draining excess fluid from the pleura) takes only 15 minutes. A healthcare professional can conduct this simple test from a doctor's office or a hospital bed. Patients do not need any preparation. The test results take about one or two working days. For infections such as tuberculosis, the results might take weeks. 

An unusual amount of pleural fluid (more than 20 millilitres) in the human body leads to a medical condition known as pleural effusion. Symptoms such as unproductive dry cough, excessive chest pain, unexplained fatigue, or difficulty breathing prevail. It is essential to drain excess liquid to avoid further complications and diagnose the root cause.

Sometimes, pleural fluid test results alone are not enough to diagnose an underlying medical condition. Doctors compare it to other tests such as glucose markers and albumin (a protein formed by the liver). Healthcare professionals use a medical determiner known as Light’s criteria to evaluate the type of pleural effusion a patient suffers from.   

Are you wondering what the pleural fluid analysis test results mean? Get a free second opinion from our experts at Yashoda Hospitals today.