Definition

Pleural fluid analysis is an examination of the pleural fluid to diagnose and treat problems in the lungs such as pleural effusion and pleuritis.  

The lungs are protected by membranes called pleura. Pleura is a vital organ in the respiratory tract. Its role is to protect the lungs and reduce any friction that may occur between the lung, rib cage, and chest cavity. 

Each pleura has two layers membrane that covers the lung, the visceral pleura that lines the lungs, and parietal pleura that lines the inside of the chest cavity. Between these two types of pleural membranes, a pleural cavity or pleural space is formed.

The pleural cavity contains pleural fluid that serves to lubricate and help maximize lung contractions when you breathe. Normally, there is only a small amount of fluid in the pleural space, which is 0.1-0.2 mL per kilogram of our body weight.

However, there are conditions when pleural fluid becomes too much or accumulates, called pleural effusion. Pleural effusion makes it difficult for the lungs to expand fully, so it is hard for you to breathe.

A pleural fluid examination helps to find the cause of pleural effusion or inflammation of the pleura. In addition, this examination can also help to determine the appropriate treatment.

Pleural fluid analysis generally includes several tests such as:

• Physical quality examination of pleural fluid such as color and viscosity
• Chemical examination to determine any changes in the chemical components of the pleural fluid
• Microscopic analysis to determine the presence of fungi, bacteria and other components.

Indications

A pleural fluid examination is recommended if on an MRI or chest X-ray the doctor assesses fluid buildup in the lung or if you experience symptoms of pleural effusion or pleuritis, such as:

• Shortness of breath
• Chest pain especially when taking a deep breath
• Cough
• Fever

In addition, pleural fluid examination can also be done to:

• Assess the presence or absence of cancer cells
• Assess other cells (such as blood cells)
• Assess levels of glucose, protein and other chemicals
• Assess the presence of bacteria, fungi, viruses or other microorganism causing infection
• Assess the inflammatory process

Contraindication

There are no contraindications or conditions that prevent a person from taking this test.

Preparations Prior to Test

There is no special preparation before the pleural fluid analysis. This examination can be done without fasting. However, you are advised to consult your doctor before doing the pleural fluid analysis because there are certain conditions that may interfere with the laboratory results so that they do not reflect your true condition.

Inform your doctor if you are taking blood-thinning medications, such as aspirin, warfarin or clopidrogel as they may affect the results.

Test Procedures 

The pleural fluid examination uses a sample of pleural fluid, this procedure is called thoracocentesis (thoracentesis). This pleural fluid sample is taken from the pleural cavity in the lungs and will be collected into a special container. Laboratory staff will wear gloves and PPE (Personal Protective Equipment) when taking the examination sample. Typically, the sample collection procedure is conducted while seated.

Before collecting the pleural fluid, the laboratory staff will clean the needle stick area with antiseptic swabs. The officer will also give anesthesia to cause a numbing effect on the skin so you do not feel pain during the sampling procedure.

After the pleural fluid is taken and put into a special tube, the officer will press and clean the puncture area with antiseptic swabs. This examination procedure only lasts for a few minutes. The pleural fluid samples that have been obtained will be examined using special equipment in the laboratory, and the results can be known within a few days.

Normal And Abnormal Values

Typically, the pleural cavity contains less than 20 milliliters (± 4 teaspoons) of clear, yellowish (serous) fluid. In cases of pleural effusion, pleural fluid analysis yields two distinct results: transudate and exudate, each of which can elucidate the underlying cause.

Transudate

Transudate refers to a thin fluid with low protein levels, resulting from increased pressure within the blood vessels. This pressure results in fluid leaking from the blood vessels into the pleural cavity. Transudate fluid may occur due to:

• Heart failure
• Kidney disease
• Liver disease, including cirrhosis

Exudate

Exudate, characterized by a turbid consistency and elevated protein levels, may arise from conditions involving inflammation, infections, and disorders affecting blood vessels or lymphatic vessels. These conditions include: 

• Pancreatitis
• Specific autoimmune disorders like rheumatoid arthritis and lupus
• Cancer, particularly leukemia, lymphoma, breast, or lung cancer
• Lung diseases that aren't cancer, including infections, such as pneumonia or tuberculosis
• Injuries to the lung or chest

Results and Suggestions (Follow-up Test)

Normal 

If your pleural fluid test results show normal values, it is likely that you have been living a healthy lifestyle and there are no abnormalities related to the lung if there are no specific symptoms and clinical signs.

You are advised to maintain your current healthy lifestyle so you can prevent lung diseases, such as pleural effusion, pleuritis, or pneumonia characterized by the discovery of abnormal parameters.

Abnormal

If the pleural fluid analysis shows abnormal results, such as:

• The presence of bacteria or fungi
• The presence of cancer cells
• Presence of pus or blood
• Lymphatic fluid is found

You should consult your doctor immediately. Your doctor may suggest changes to a healthier diet and lifestyle, or even start drug therapy to help manage symptoms related to lung disease.

Consult To The Right Doctor

The results of pleural fluid analysis in adults can be consulted with a general practitioner, for further examination or to start therapy for an appropriate diagnosis. You can also consult a pulmonologist or internal medicine specialist to discuss your pleural fluid problem further. In pediatric patients, examination results other than normal should be consulted with a pediatrician.